Display exception notes in tracebacks (#14039)

[PEP 678](https://peps.python.org/pep-0678/) introduced the ability to
add notes to exception objects. This has been [released in Python
3.11](https://docs.python.org/3/library/exceptions.html#BaseException.add_note)
and is currently not implemented in IPython. These changes are fully
compatible with older Python versions that don't include PEP 678.

Here's a sample test that shows the consistency in Python's stdlib
traceback module (test 1) and the difference between Python and
IPython's runtimes (test 2):
```python
import traceback

print('--- test 1 ---')
try:
    raise Exception('Testing notes')
except Exception as e:
    e.add_note('Does this work?')
    e.add_note('Yes!')
    traceback.print_exc()

print('\n--- test 2 ---')
try:
    raise Exception('Testing notes')
except Exception as e:
    e.add_note('Does this work?')
    e.add_note('No!')
    raise
```

When executed with Python 3.11, both notes are displayed in both
tracebacks:
```
$ python test.py 
--- test 1 ---
Traceback (most recent call last):
  File "/app/test.py", line 5, in <module>
    raise Exception('Testing notes')
Exception: Testing notes
Does this work?
Yes!

--- test 2 ---
Traceback (most recent call last):
  File "/app/test.py", line 13, in <module>
    raise Exception('Testing notes')
Exception: Testing notes
Does this work?
No!
```

In IPython's VerboseTB does not yet handle exception notes:
```
$ ipython test.py 
--- test 1 ---
Traceback (most recent call last):
  File "/app/test.py", line 5, in <module>
    raise Exception('Testing notes')
Exception: Testing notes
Does this work?
Yes!

--- test 2 ---
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
File /app/test.py:13
     11 print('\n--- test 2 ---')
     12 try:
---> 13     raise Exception('Testing notes')
     14 except Exception as e:
     15     e.add_note('Does this work?')

Exception: Testing notes
```

The changes I am suggesting are inspired from implementation of
[Lib/traceback.py](https://github.com/python/cpython/blob/main/Lib/traceback.py)
(search for `__notes__`) and improvements for dealing with edge cases
more nicely in
[cpython#103897](https://github.com/python/cpython/pull/103897).

Although notes are meant to be strings only, I kept some inspiration
from the existing exception handling to ensure that the notes are
uncolored and bytes decoded, if there are any. I am definitely open to
using a different color if deemed better. For context, `bpython` keeps
the notes uncolored, and [Python's
tutorial](https://docs.python.org/3/tutorial/errors.html#enriching-exceptions-with-notes)
puts them in light gray, like the line numbers.

Here's how the test 2 looks like after these changes:

![image](https://user-images.githubusercontent.com/16963011/234723689-6bbfe0ff-94d4-4a90-9da6-acfe1c8e5edf.png)

## :snake: :man_juggling:

docs/source/whatsnew/pr/pep678-notes.rst

@@ -0,0 +1,5 b''
+Support for PEP-678 Exception Notes
+-----------------------------------
+
+Ultratb now shows :pep:`678` notes, improving your debugging experience on
+Python 3.11+ or with libraries such as Pytest and Hypothesis.

.gitignore

@@ -1,40 +1,41 b''
 MANIFEST
 build
 dist
 _build
 docs/man/*.gz
 docs/source/api/generated
 docs/source/config/options
 docs/source/config/shortcuts/*.csv
 docs/source/config/shortcuts/table.tsv
 docs/source/savefig
 docs/source/interactive/magics-generated.txt
 docs/gh-pages
 jupyter_notebook/notebook/static/mathjax
 jupyter_notebook/static/style/*.map
 *.py[co]
 __pycache__
 *.egg-info
 *~
 *.bak
 .ipynb_checkpoints
 .tox
 .DS_Store
 \#*#
 .#*
 .cache
 .coverage
 *.swp
 .pytest_cache
 .python-version
+.venv*/
 venv*/
 .mypy_cache/
 
 # jetbrains ide stuff
 *.iml
 .idea/
 
 # vscode ide stuff
 *.code-workspace
 .history
 .vscode

IPython/core/tests/test_ultratb.py

@@ -1,407 +1,430 b''
 # encoding: utf-8
 """Tests for IPython.core.ultratb
 """
 import io
 import os.path
 import platform
 import re
 import sys
 import traceback
 import unittest
 from textwrap import dedent
 
 from tempfile import TemporaryDirectory
 
 from IPython.core.ultratb import ColorTB, VerboseTB
 from IPython.testing import tools as tt
 from IPython.testing.decorators import onlyif_unicode_paths
 from IPython.utils.syspathcontext import prepended_to_syspath
 
 file_1 = """1
 2
 3
 def f():
   1/0
 """
 
 file_2 = """def f():
   1/0
 """
 
 
 def recursionlimit(frames):
     """
     decorator to set the recursion limit temporarily
     """
 
     def inner(test_function):
         def wrapper(*args, **kwargs):
             rl = sys.getrecursionlimit()
             sys.setrecursionlimit(frames)
             try:
                 return test_function(*args, **kwargs)
             finally:
                 sys.setrecursionlimit(rl)
 
         return wrapper
 
     return inner
 
 
 class ChangedPyFileTest(unittest.TestCase):
     def test_changing_py_file(self):
         """Traceback produced if the line where the error occurred is missing?
-        
+
         https://github.com/ipython/ipython/issues/1456
         """
         with TemporaryDirectory() as td:
             fname = os.path.join(td, "foo.py")
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(file_1)
-            
+
             with prepended_to_syspath(td):
                 ip.run_cell("import foo")
-            
+
             with tt.AssertPrints("ZeroDivisionError"):
                 ip.run_cell("foo.f()")
-            
+
             # Make the file shorter, so the line of the error is missing.
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(file_2)
-            
+
             # For some reason, this was failing on the *second* call after
             # changing the file, so we call f() twice.
             with tt.AssertNotPrints("Internal Python error", channel='stderr'):
                 with tt.AssertPrints("ZeroDivisionError"):
                     ip.run_cell("foo.f()")
                 with tt.AssertPrints("ZeroDivisionError"):
                     ip.run_cell("foo.f()")
 
 iso_8859_5_file = u'''# coding: iso-8859-5
 
 def fail():
     """дбИЖ"""
     1/0     # дбИЖ
 '''
 
 class NonAsciiTest(unittest.TestCase):
     @onlyif_unicode_paths
     def test_nonascii_path(self):
         # Non-ascii directory name as well.
         with TemporaryDirectory(suffix=u'é') as td:
             fname = os.path.join(td, u"fooé.py")
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(file_1)
-            
+
             with prepended_to_syspath(td):
                 ip.run_cell("import foo")
-            
+
             with tt.AssertPrints("ZeroDivisionError"):
                 ip.run_cell("foo.f()")
-    
+
     def test_iso8859_5(self):
         with TemporaryDirectory() as td:
             fname = os.path.join(td, 'dfghjkl.py')
 
             with io.open(fname, 'w', encoding='iso-8859-5') as f:
                 f.write(iso_8859_5_file)
-            
+
             with prepended_to_syspath(td):
                 ip.run_cell("from dfghjkl import fail")
-            
+
             with tt.AssertPrints("ZeroDivisionError"):
                 with tt.AssertPrints(u'дбИЖ', suppress=False):
                     ip.run_cell('fail()')
-    
+
     def test_nonascii_msg(self):
         cell = u"raise Exception('é')"
         expected = u"Exception('é')"
         ip.run_cell("%xmode plain")
         with tt.AssertPrints(expected):
             ip.run_cell(cell)
 
         ip.run_cell("%xmode verbose")
         with tt.AssertPrints(expected):
             ip.run_cell(cell)
 
         ip.run_cell("%xmode context")
         with tt.AssertPrints(expected):
             ip.run_cell(cell)
 
         ip.run_cell("%xmode minimal")
         with tt.AssertPrints(u"Exception: é"):
             ip.run_cell(cell)
 
         # Put this back into Context mode for later tests.
         ip.run_cell("%xmode context")
 
 class NestedGenExprTestCase(unittest.TestCase):
     """
     Regression test for the following issues:
     https://github.com/ipython/ipython/issues/8293
     https://github.com/ipython/ipython/issues/8205
     """
     def test_nested_genexpr(self):
         code = dedent(
             """\
             class SpecificException(Exception):
                 pass
 
             def foo(x):
                 raise SpecificException("Success!")
 
             sum(sum(foo(x) for _ in [0]) for x in [0])
             """
         )
         with tt.AssertPrints('SpecificException: Success!', suppress=False):
             ip.run_cell(code)
 
 
 indentationerror_file = """if True:
 zoon()
 """
 
 class IndentationErrorTest(unittest.TestCase):
     def test_indentationerror_shows_line(self):
         # See issue gh-2398
         with tt.AssertPrints("IndentationError"):
             with tt.AssertPrints("zoon()", suppress=False):
                 ip.run_cell(indentationerror_file)
-        
+
         with TemporaryDirectory() as td:
             fname = os.path.join(td, "foo.py")
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(indentationerror_file)
-            
+
             with tt.AssertPrints("IndentationError"):
                 with tt.AssertPrints("zoon()", suppress=False):
                     ip.magic('run %s' % fname)
 
 se_file_1 = """1
 2
 7/
 """
 
 se_file_2 = """7/
 """
 
 class SyntaxErrorTest(unittest.TestCase):
 
     def test_syntaxerror_no_stacktrace_at_compile_time(self):
         syntax_error_at_compile_time = """
 def foo():
     ..
 """
         with tt.AssertPrints("SyntaxError"):
             ip.run_cell(syntax_error_at_compile_time)
 
         with tt.AssertNotPrints("foo()"):
             ip.run_cell(syntax_error_at_compile_time)
 
     def test_syntaxerror_stacktrace_when_running_compiled_code(self):
         syntax_error_at_runtime = """
 def foo():
     eval("..")
 
 def bar():
     foo()
 
 bar()
 """
         with tt.AssertPrints("SyntaxError"):
             ip.run_cell(syntax_error_at_runtime)
         # Assert syntax error during runtime generate stacktrace
         with tt.AssertPrints(["foo()", "bar()"]):
             ip.run_cell(syntax_error_at_runtime)
         del ip.user_ns['bar']
         del ip.user_ns['foo']
 
     def test_changing_py_file(self):
         with TemporaryDirectory() as td:
             fname = os.path.join(td, "foo.py")
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(se_file_1)
 
             with tt.AssertPrints(["7/", "SyntaxError"]):
                 ip.magic("run " + fname)
 
             # Modify the file
             with open(fname, "w", encoding="utf-8") as f:
                 f.write(se_file_2)
 
             # The SyntaxError should point to the correct line
             with tt.AssertPrints(["7/", "SyntaxError"]):
                 ip.magic("run " + fname)
 
     def test_non_syntaxerror(self):
         # SyntaxTB may be called with an error other than a SyntaxError
         # See e.g. gh-4361
         try:
             raise ValueError('QWERTY')
         except ValueError:
             with tt.AssertPrints('QWERTY'):
                 ip.showsyntaxerror()
 
 import sys
 
 if platform.python_implementation() != "PyPy":
     """
     New 3.9 Pgen Parser does not raise Memory error, except on failed malloc.
     """
     class MemoryErrorTest(unittest.TestCase):
         def test_memoryerror(self):
             memoryerror_code = "(" * 200 + ")" * 200
             ip.run_cell(memoryerror_code)
 
 
 class Python3ChainedExceptionsTest(unittest.TestCase):
     DIRECT_CAUSE_ERROR_CODE = """
 try:
     x = 1 + 2
     print(not_defined_here)
 except Exception as e:
     x += 55
     x - 1
     y = {}
     raise KeyError('uh') from e
     """
 
     EXCEPTION_DURING_HANDLING_CODE = """
 try:
     x = 1 + 2
     print(not_defined_here)
 except Exception as e:
     x += 55
     x - 1
     y = {}
     raise KeyError('uh')
     """
 
     SUPPRESS_CHAINING_CODE = """
 try:
     1/0
 except Exception:
     raise ValueError("Yikes") from None
     """
 
     def test_direct_cause_error(self):
         with tt.AssertPrints(["KeyError", "NameError", "direct cause"]):
             ip.run_cell(self.DIRECT_CAUSE_ERROR_CODE)
 
     def test_exception_during_handling_error(self):
         with tt.AssertPrints(["KeyError", "NameError", "During handling"]):
             ip.run_cell(self.EXCEPTION_DURING_HANDLING_CODE)
 
     def test_suppress_exception_chaining(self):
         with tt.AssertNotPrints("ZeroDivisionError"), \
              tt.AssertPrints("ValueError", suppress=False):
             ip.run_cell(self.SUPPRESS_CHAINING_CODE)
 
     def test_plain_direct_cause_error(self):
         with tt.AssertPrints(["KeyError", "NameError", "direct cause"]):
             ip.run_cell("%xmode Plain")
             ip.run_cell(self.DIRECT_CAUSE_ERROR_CODE)
             ip.run_cell("%xmode Verbose")
 
     def test_plain_exception_during_handling_error(self):
         with tt.AssertPrints(["KeyError", "NameError", "During handling"]):
             ip.run_cell("%xmode Plain")
             ip.run_cell(self.EXCEPTION_DURING_HANDLING_CODE)
             ip.run_cell("%xmode Verbose")
 
     def test_plain_suppress_exception_chaining(self):
         with tt.AssertNotPrints("ZeroDivisionError"), \
              tt.AssertPrints("ValueError", suppress=False):
             ip.run_cell("%xmode Plain")
             ip.run_cell(self.SUPPRESS_CHAINING_CODE)
             ip.run_cell("%xmode Verbose")
 
 
 class RecursionTest(unittest.TestCase):
     DEFINITIONS = """
 def non_recurs():
     1/0
 
 def r1():
     r1()
 
 def r3a():
     r3b()
 
 def r3b():
     r3c()
 
 def r3c():
     r3a()
 
 def r3o1():
     r3a()
 
 def r3o2():
     r3o1()
 """
     def setUp(self):
         ip.run_cell(self.DEFINITIONS)
 
     def test_no_recursion(self):
         with tt.AssertNotPrints("skipping similar frames"):
             ip.run_cell("non_recurs()")
 
     @recursionlimit(200)
     def test_recursion_one_frame(self):
         with tt.AssertPrints(re.compile(
             r"\[\.\.\. skipping similar frames: r1 at line 5 \(\d{2,3} times\)\]")
         ):
             ip.run_cell("r1()")
 
     @recursionlimit(160)
     def test_recursion_three_frames(self):
         with tt.AssertPrints("[... skipping similar frames: "), \
                 tt.AssertPrints(re.compile(r"r3a at line 8 \(\d{2} times\)"), suppress=False), \
                 tt.AssertPrints(re.compile(r"r3b at line 11 \(\d{2} times\)"), suppress=False), \
                 tt.AssertPrints(re.compile(r"r3c at line 14 \(\d{2} times\)"), suppress=False):
             ip.run_cell("r3o2()")
 
 
+class PEP678NotesReportingTest(unittest.TestCase):
+    ERROR_WITH_NOTE = """
+try:
+    raise AssertionError("Message")
+except Exception as e:
+    try:
+        e.add_note("This is a PEP-678 note.")
+    except AttributeError:  # Python <= 3.10
+        e.__notes__ = ("This is a PEP-678 note.",)
+    raise
+    """
+
+    def test_verbose_reports_notes(self):
+        with tt.AssertPrints(["AssertionError", "Message", "This is a PEP-678 note."]):
+            ip.run_cell(self.ERROR_WITH_NOTE)
+
+    def test_plain_reports_notes(self):
+        with tt.AssertPrints(["AssertionError", "Message", "This is a PEP-678 note."]):
+            ip.run_cell("%xmode Plain")
+            ip.run_cell(self.ERROR_WITH_NOTE)
+            ip.run_cell("%xmode Verbose")
+
+
 #----------------------------------------------------------------------------
 
 # module testing (minimal)
 def test_handlers():
     def spam(c, d_e):
         (d, e) = d_e
         x = c + d
         y = c * d
         foo(x, y)
 
     def foo(a, b, bar=1):
         eggs(a, b + bar)
 
     def eggs(f, g, z=globals()):
         h = f + g
         i = f - g
         return h / i
 
     buff = io.StringIO()
 
     buff.write('')
     buff.write('*** Before ***')
     try:
         buff.write(spam(1, (2, 3)))
     except:
         traceback.print_exc(file=buff)
 
     handler = ColorTB(ostream=buff)
     buff.write('*** ColorTB ***')
     try:
         buff.write(spam(1, (2, 3)))
     except:
         handler(*sys.exc_info())
     buff.write('')
 
     handler = VerboseTB(ostream=buff)
     buff.write('*** VerboseTB ***')
     try:
         buff.write(spam(1, (2, 3)))
     except:
         handler(*sys.exc_info())
     buff.write('')

IPython/core/ultratb.py

@@ -1,1486 +1,1518 b''
 # -*- coding: utf-8 -*-
 """
 Verbose and colourful traceback formatting.
 
 **ColorTB**
 
 I've always found it a bit hard to visually parse tracebacks in Python.  The
 ColorTB class is a solution to that problem.  It colors the different parts of a
 traceback in a manner similar to what you would expect from a syntax-highlighting
 text editor.
 
 Installation instructions for ColorTB::
 
     import sys,ultratb
     sys.excepthook = ultratb.ColorTB()
 
 **VerboseTB**
 
 I've also included a port of Ka-Ping Yee's "cgitb.py" that produces all kinds
 of useful info when a traceback occurs.  Ping originally had it spit out HTML
 and intended it for CGI programmers, but why should they have all the fun?  I
 altered it to spit out colored text to the terminal.  It's a bit overwhelming,
 but kind of neat, and maybe useful for long-running programs that you believe
 are bug-free.  If a crash *does* occur in that type of program you want details.
 Give it a shot--you'll love it or you'll hate it.
 
 .. note::
 
   The Verbose mode prints the variables currently visible where the exception
   happened (shortening their strings if too long). This can potentially be
   very slow, if you happen to have a huge data structure whose string
   representation is complex to compute. Your computer may appear to freeze for
   a while with cpu usage at 100%. If this occurs, you can cancel the traceback
   with Ctrl-C (maybe hitting it more than once).
 
   If you encounter this kind of situation often, you may want to use the
   Verbose_novars mode instead of the regular Verbose, which avoids formatting
   variables (but otherwise includes the information and context given by
   Verbose).
 
 .. note::
 
   The verbose mode print all variables in the stack, which means it can
   potentially leak sensitive information like access keys, or unencrypted
   password.
 
 Installation instructions for VerboseTB::
 
     import sys,ultratb
     sys.excepthook = ultratb.VerboseTB()
 
 Note:  Much of the code in this module was lifted verbatim from the standard
 library module 'traceback.py' and Ka-Ping Yee's 'cgitb.py'.
 
 Color schemes
 -------------
 
 The colors are defined in the class TBTools through the use of the
 ColorSchemeTable class. Currently the following exist:
 
   - NoColor: allows all of this module to be used in any terminal (the color
     escapes are just dummy blank strings).
 
   - Linux: is meant to look good in a terminal like the Linux console (black
     or very dark background).
 
   - LightBG: similar to Linux but swaps dark/light colors to be more readable
     in light background terminals.
 
   - Neutral: a neutral color scheme that should be readable on both light and
     dark background
 
 You can implement other color schemes easily, the syntax is fairly
 self-explanatory. Please send back new schemes you develop to the author for
 possible inclusion in future releases.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.core.ultratb
    :parts: 3
 """
 
 #*****************************************************************************
 # Copyright (C) 2001 Nathaniel Gray <[e-mail]>
 # Copyright (C) 2001-2004 Fernando Perez <[e-mail]>
 #
 # Distributed under the terms of the BSD License.  The full license is in
 # the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 
+from collections.abc import Sequence
 import functools
 import inspect
 import linecache
 import pydoc
 import sys
 import time
 import traceback
 import types
 from types import TracebackType
 from typing import Any, List, Optional, Tuple
 
 import stack_data
 from pygments.formatters.terminal256 import Terminal256Formatter
 from pygments.styles import get_style_by_name
 
 import IPython.utils.colorable as colorable
 # IPython's own modules
 from IPython import get_ipython
 from IPython.core import debugger
 from IPython.core.display_trap import DisplayTrap
 from IPython.core.excolors import exception_colors
 from IPython.utils import PyColorize
 from IPython.utils import path as util_path
 from IPython.utils import py3compat
 from IPython.utils.terminal import get_terminal_size
 
 # Globals
 # amount of space to put line numbers before verbose tracebacks
 INDENT_SIZE = 8
 
 # Default color scheme.  This is used, for example, by the traceback
 # formatter.  When running in an actual IPython instance, the user's rc.colors
 # value is used, but having a module global makes this functionality available
 # to users of ultratb who are NOT running inside ipython.
 DEFAULT_SCHEME = 'NoColor'
 FAST_THRESHOLD = 10_000
 
 # ---------------------------------------------------------------------------
 # Code begins
 
 # Helper function -- largely belongs to VerboseTB, but we need the same
 # functionality to produce a pseudo verbose TB for SyntaxErrors, so that they
 # can be recognized properly by ipython.el's py-traceback-line-re
 # (SyntaxErrors have to be treated specially because they have no traceback)
 
 
 @functools.lru_cache()
 def count_lines_in_py_file(filename: str) -> int:
     """
     Given a filename, returns the number of lines in the file
     if it ends with the extension ".py". Otherwise, returns 0.
     """
     if not filename.endswith(".py"):
         return 0
     else:
         try:
             with open(filename, "r") as file:
                 s = sum(1 for line in file)
         except UnicodeError:
             return 0
     return s
 
     """
     Given a frame object, returns the total number of lines in the file
     if the filename ends with the extension ".py". Otherwise, returns 0.
     """
 
 
 def get_line_number_of_frame(frame: types.FrameType) -> int:
     """
     Given a frame object, returns the total number of lines in the file
     containing the frame's code object, or the number of lines in the
     frame's source code if the file is not available.
 
     Parameters
     ----------
     frame : FrameType
         The frame object whose line number is to be determined.
 
     Returns
     -------
     int
         The total number of lines in the file containing the frame's
         code object, or the number of lines in the frame's source code
         if the file is not available.
     """
     filename = frame.f_code.co_filename
     if filename is None:
         print("No file....")
         lines, first = inspect.getsourcelines(frame)
         return first + len(lines)
     return count_lines_in_py_file(filename)
 
 
+def _safe_string(value, what, func=str):
+    # Copied from cpython/Lib/traceback.py
+    try:
+        return func(value)
+    except:
+        return f"<{what} {func.__name__}() failed>"
+
+
 def _format_traceback_lines(lines, Colors, has_colors: bool, lvals):
     """
     Format tracebacks lines with pointing arrow, leading numbers...
 
     Parameters
     ----------
     lines : list[Line]
     Colors
         ColorScheme used.
     lvals : str
         Values of local variables, already colored, to inject just after the error line.
     """
     numbers_width = INDENT_SIZE - 1
     res = []
 
     for stack_line in lines:
         if stack_line is stack_data.LINE_GAP:
             res.append('%s   (...)%s\n' % (Colors.linenoEm, Colors.Normal))
             continue
 
         line = stack_line.render(pygmented=has_colors).rstrip('\n') + '\n'
         lineno = stack_line.lineno
         if stack_line.is_current:
             # This is the line with the error
             pad = numbers_width - len(str(lineno))
             num = '%s%s' % (debugger.make_arrow(pad), str(lineno))
             start_color = Colors.linenoEm
         else:
             num = '%*s' % (numbers_width, lineno)
             start_color = Colors.lineno
 
         line = '%s%s%s %s' % (start_color, num, Colors.Normal, line)
 
         res.append(line)
         if lvals and stack_line.is_current:
             res.append(lvals + '\n')
     return res
 
 def _simple_format_traceback_lines(lnum, index, lines, Colors, lvals, _line_format):
     """
     Format tracebacks lines with pointing arrow, leading numbers...
 
     Parameters
     ==========
 
     lnum: int
         number of the target line of code.
     index: int
         which line in the list should be highlighted.
     lines: list[string]
     Colors:
         ColorScheme used.
     lvals: bytes
         Values of local variables, already colored, to inject just after the error line.
     _line_format: f (str) -> (str, bool)
         return (colorized version of str, failure to do so)
     """
     numbers_width = INDENT_SIZE - 1
     res = []
     for i, line in enumerate(lines, lnum - index):
         # assert isinstance(line, str)
         line = py3compat.cast_unicode(line)
 
         new_line, err = _line_format(line, "str")
         if not err:
             line = new_line
 
         if i == lnum:
             # This is the line with the error
             pad = numbers_width - len(str(i))
             num = "%s%s" % (debugger.make_arrow(pad), str(lnum))
             line = "%s%s%s %s%s" % (
                 Colors.linenoEm,
                 num,
                 Colors.line,
                 line,
                 Colors.Normal,
             )
         else:
             num = "%*s" % (numbers_width, i)
             line = "%s%s%s %s" % (Colors.lineno, num, Colors.Normal, line)
 
         res.append(line)
         if lvals and i == lnum:
             res.append(lvals + "\n")
     return res
 
 
 def _format_filename(file, ColorFilename, ColorNormal, *, lineno=None):
     """
     Format filename lines with custom formatting from caching compiler or `File *.py` by default
 
     Parameters
     ----------
     file : str
     ColorFilename
         ColorScheme's filename coloring to be used.
     ColorNormal
         ColorScheme's normal coloring to be used.
     """
     ipinst = get_ipython()
     if (
         ipinst is not None
         and (data := ipinst.compile.format_code_name(file)) is not None
     ):
         label, name = data
         if lineno is None:
             tpl_link = f"{{label}} {ColorFilename}{{name}}{ColorNormal}"
         else:
             tpl_link = (
                 f"{{label}} {ColorFilename}{{name}}, line {{lineno}}{ColorNormal}"
             )
     else:
         label = "File"
         name = util_path.compress_user(
             py3compat.cast_unicode(file, util_path.fs_encoding)
         )
         if lineno is None:
             tpl_link = f"{{label}} {ColorFilename}{{name}}{ColorNormal}"
         else:
             # can we make this the more friendly ", line {{lineno}}", or do we need to preserve the formatting with the colon?
             tpl_link = f"{{label}} {ColorFilename}{{name}}:{{lineno}}{ColorNormal}"
 
     return tpl_link.format(label=label, name=name, lineno=lineno)
 
 #---------------------------------------------------------------------------
 # Module classes
 class TBTools(colorable.Colorable):
     """Basic tools used by all traceback printer classes."""
 
     # Number of frames to skip when reporting tracebacks
     tb_offset = 0
 
     def __init__(
         self,
         color_scheme="NoColor",
         call_pdb=False,
         ostream=None,
         parent=None,
         config=None,
         *,
         debugger_cls=None,
     ):
         # Whether to call the interactive pdb debugger after printing
         # tracebacks or not
         super(TBTools, self).__init__(parent=parent, config=config)
         self.call_pdb = call_pdb
 
         # Output stream to write to.  Note that we store the original value in
         # a private attribute and then make the public ostream a property, so
         # that we can delay accessing sys.stdout until runtime.  The way
         # things are written now, the sys.stdout object is dynamically managed
         # so a reference to it should NEVER be stored statically.  This
         # property approach confines this detail to a single location, and all
         # subclasses can simply access self.ostream for writing.
         self._ostream = ostream
 
         # Create color table
         self.color_scheme_table = exception_colors()
 
         self.set_colors(color_scheme)
         self.old_scheme = color_scheme  # save initial value for toggles
         self.debugger_cls = debugger_cls or debugger.Pdb
 
         if call_pdb:
             self.pdb = self.debugger_cls()
         else:
             self.pdb = None
 
     def _get_ostream(self):
         """Output stream that exceptions are written to.
 
         Valid values are:
 
         - None: the default, which means that IPython will dynamically resolve
           to sys.stdout.  This ensures compatibility with most tools, including
           Windows (where plain stdout doesn't recognize ANSI escapes).
 
         - Any object with 'write' and 'flush' attributes.
         """
         return sys.stdout if self._ostream is None else self._ostream
 
     def _set_ostream(self, val):
         assert val is None or (hasattr(val, 'write') and hasattr(val, 'flush'))
         self._ostream = val
 
     ostream = property(_get_ostream, _set_ostream)
 
     @staticmethod
     def _get_chained_exception(exception_value):
         cause = getattr(exception_value, "__cause__", None)
         if cause:
             return cause
         if getattr(exception_value, "__suppress_context__", False):
             return None
         return getattr(exception_value, "__context__", None)
 
     def get_parts_of_chained_exception(
         self, evalue
     ) -> Optional[Tuple[type, BaseException, TracebackType]]:
         chained_evalue = self._get_chained_exception(evalue)
 
         if chained_evalue:
             return chained_evalue.__class__, chained_evalue, chained_evalue.__traceback__
         return None
 
     def prepare_chained_exception_message(self, cause) -> List[Any]:
         direct_cause = "\nThe above exception was the direct cause of the following exception:\n"
         exception_during_handling = "\nDuring handling of the above exception, another exception occurred:\n"
 
         if cause:
             message = [[direct_cause]]
         else:
             message = [[exception_during_handling]]
         return message
 
     @property
     def has_colors(self) -> bool:
         return self.color_scheme_table.active_scheme_name.lower() != "nocolor"
 
     def set_colors(self, *args, **kw):
         """Shorthand access to the color table scheme selector method."""
 
         # Set own color table
         self.color_scheme_table.set_active_scheme(*args, **kw)
         # for convenience, set Colors to the active scheme
         self.Colors = self.color_scheme_table.active_colors
         # Also set colors of debugger
         if hasattr(self, 'pdb') and self.pdb is not None:
             self.pdb.set_colors(*args, **kw)
 
     def color_toggle(self):
         """Toggle between the currently active color scheme and NoColor."""
 
         if self.color_scheme_table.active_scheme_name == 'NoColor':
             self.color_scheme_table.set_active_scheme(self.old_scheme)
             self.Colors = self.color_scheme_table.active_colors
         else:
             self.old_scheme = self.color_scheme_table.active_scheme_name
             self.color_scheme_table.set_active_scheme('NoColor')
             self.Colors = self.color_scheme_table.active_colors
 
     def stb2text(self, stb):
         """Convert a structured traceback (a list) to a string."""
         return '\n'.join(stb)
 
     def text(self, etype, value, tb, tb_offset: Optional[int] = None, context=5):
         """Return formatted traceback.
 
         Subclasses may override this if they add extra arguments.
         """
         tb_list = self.structured_traceback(etype, value, tb,
                                             tb_offset, context)
         return self.stb2text(tb_list)
 
     def structured_traceback(
         self,
         etype: type,
         evalue: Optional[BaseException],
         etb: Optional[TracebackType] = None,
         tb_offset: Optional[int] = None,
         number_of_lines_of_context: int = 5,
     ):
         """Return a list of traceback frames.
 
         Must be implemented by each class.
         """
         raise NotImplementedError()
 
 
 #---------------------------------------------------------------------------
 class ListTB(TBTools):
     """Print traceback information from a traceback list, with optional color.
 
     Calling requires 3 arguments: (etype, evalue, elist)
     as would be obtained by::
 
       etype, evalue, tb = sys.exc_info()
       if tb:
         elist = traceback.extract_tb(tb)
       else:
         elist = None
 
     It can thus be used by programs which need to process the traceback before
     printing (such as console replacements based on the code module from the
     standard library).
 
     Because they are meant to be called without a full traceback (only a
     list), instances of this class can't call the interactive pdb debugger."""
 
 
     def __call__(self, etype, value, elist):
         self.ostream.flush()
         self.ostream.write(self.text(etype, value, elist))
         self.ostream.write('\n')
 
     def _extract_tb(self, tb):
         if tb:
             return traceback.extract_tb(tb)
         else:
             return None
 
     def structured_traceback(
         self,
         etype: type,
         evalue: Optional[BaseException],
         etb: Optional[TracebackType] = None,
         tb_offset: Optional[int] = None,
         context=5,
     ):
         """Return a color formatted string with the traceback info.
 
         Parameters
         ----------
         etype : exception type
             Type of the exception raised.
         evalue : object
             Data stored in the exception
         etb : list | TracebackType | None
             If list: List of frames, see class docstring for details.
             If Traceback: Traceback of the exception.
         tb_offset : int, optional
             Number of frames in the traceback to skip.  If not given, the
             instance evalue is used (set in constructor).
         context : int, optional
             Number of lines of context information to print.
 
         Returns
         -------
         String with formatted exception.
         """
         # This is a workaround to get chained_exc_ids in recursive calls
         # etb should not be a tuple if structured_traceback is not recursive
         if isinstance(etb, tuple):
             etb, chained_exc_ids = etb
         else:
             chained_exc_ids = set()
 
         if isinstance(etb, list):
             elist = etb
         elif etb is not None:
             elist = self._extract_tb(etb)
         else:
             elist = []
         tb_offset = self.tb_offset if tb_offset is None else tb_offset
         assert isinstance(tb_offset, int)
         Colors = self.Colors
         out_list = []
         if elist:
 
             if tb_offset and len(elist) > tb_offset:
                 elist = elist[tb_offset:]
 
             out_list.append('Traceback %s(most recent call last)%s:' %
                             (Colors.normalEm, Colors.Normal) + '\n')
             out_list.extend(self._format_list(elist))
         # The exception info should be a single entry in the list.
         lines = ''.join(self._format_exception_only(etype, evalue))
         out_list.append(lines)
 
         exception = self.get_parts_of_chained_exception(evalue)
 
         if exception and (id(exception[1]) not in chained_exc_ids):
             chained_exception_message = (
                 self.prepare_chained_exception_message(evalue.__cause__)[0]
                 if evalue is not None
                 else ""
             )
             etype, evalue, etb = exception
             # Trace exception to avoid infinite 'cause' loop
             chained_exc_ids.add(id(exception[1]))
             chained_exceptions_tb_offset = 0
             out_list = (
                 self.structured_traceback(
                     etype,
                     evalue,
                     (etb, chained_exc_ids),  # type: ignore
                     chained_exceptions_tb_offset,
                     context,
                 )
                 + chained_exception_message
                 + out_list)
 
         return out_list
 
     def _format_list(self, extracted_list):
         """Format a list of traceback entry tuples for printing.
 
         Given a list of tuples as returned by extract_tb() or
         extract_stack(), return a list of strings ready for printing.
         Each string in the resulting list corresponds to the item with the
         same index in the argument list.  Each string ends in a newline;
         the strings may contain internal newlines as well, for those items
         whose source text line is not None.
 
         Lifted almost verbatim from traceback.py
         """
 
         Colors = self.Colors
-        list = []
+        output_list = []
         for ind, (filename, lineno, name, line) in enumerate(extracted_list):
             normalCol, nameCol, fileCol, lineCol = (
                 # Emphasize the last entry
                 (Colors.normalEm, Colors.nameEm, Colors.filenameEm, Colors.line)
                 if ind == len(extracted_list) - 1
                 else (Colors.Normal, Colors.name, Colors.filename, "")
             )
 
             fns = _format_filename(filename, fileCol, normalCol, lineno=lineno)
             item = f"{normalCol}  {fns}"
 
             if name != "<module>":
                 item += f" in {nameCol}{name}{normalCol}\n"
             else:
                 item += "\n"
             if line:
                 item += f"{lineCol}    {line.strip()}{normalCol}\n"
-            list.append(item)
+            output_list.append(item)
 
-        return list
+        return output_list
 
     def _format_exception_only(self, etype, value):
         """Format the exception part of a traceback.
 
         The arguments are the exception type and value such as given by
         sys.exc_info()[:2]. The return value is a list of strings, each ending
         in a newline.  Normally, the list contains a single string; however,
         for SyntaxError exceptions, it contains several lines that (when
         printed) display detailed information about where the syntax error
         occurred.  The message indicating which exception occurred is the
         always last string in the list.
 
         Also lifted nearly verbatim from traceback.py
         """
         have_filedata = False
         Colors = self.Colors
-        list = []
+        output_list = []
         stype = py3compat.cast_unicode(Colors.excName + etype.__name__ + Colors.Normal)
         if value is None:
             # Not sure if this can still happen in Python 2.6 and above
-            list.append(stype + '\n')
+            output_list.append(stype + "\n")
         else:
             if issubclass(etype, SyntaxError):
                 have_filedata = True
                 if not value.filename: value.filename = "<string>"
                 if value.lineno:
                     lineno = value.lineno
                     textline = linecache.getline(value.filename, value.lineno)
                 else:
                     lineno = "unknown"
                     textline = ""
-                list.append(
+                output_list.append(
                     "%s  %s%s\n"
                     % (
                         Colors.normalEm,
                         _format_filename(
                             value.filename,
                             Colors.filenameEm,
                             Colors.normalEm,
                             lineno=(None if lineno == "unknown" else lineno),
                         ),
                         Colors.Normal,
                     )
                 )
                 if textline == "":
                     textline = py3compat.cast_unicode(value.text, "utf-8")
 
                 if textline is not None:
                     i = 0
                     while i < len(textline) and textline[i].isspace():
                         i += 1
-                    list.append('%s    %s%s\n' % (Colors.line,
-                                                  textline.strip(),
-                                                  Colors.Normal))
+                    output_list.append(
+                        "%s    %s%s\n" % (Colors.line, textline.strip(), Colors.Normal)
+                    )
                     if value.offset is not None:
                         s = '    '
                         for c in textline[i:value.offset - 1]:
                             if c.isspace():
                                 s += c
                             else:
-                                s += ' '
-                        list.append('%s%s^%s\n' % (Colors.caret, s,
-                                                   Colors.Normal))
+                                s += " "
+                        output_list.append(
+                            "%s%s^%s\n" % (Colors.caret, s, Colors.Normal)
+                        )
 
             try:
                 s = value.msg
             except Exception:
                 s = self._some_str(value)
             if s:
-                list.append('%s%s:%s %s\n' % (stype, Colors.excName,
-                                              Colors.Normal, s))
+                output_list.append(
+                    "%s%s:%s %s\n" % (stype, Colors.excName, Colors.Normal, s)
+                )
             else:
-                list.append('%s\n' % stype)
+                output_list.append("%s\n" % stype)
+
+            # PEP-678 notes
+            output_list.extend(f"{x}\n" for x in getattr(value, "__notes__", []))
 
         # sync with user hooks
         if have_filedata:
             ipinst = get_ipython()
             if ipinst is not None:
                 ipinst.hooks.synchronize_with_editor(value.filename, value.lineno, 0)
 
-        return list
+        return output_list
 
     def get_exception_only(self, etype, value):
         """Only print the exception type and message, without a traceback.
 
         Parameters
         ----------
         etype : exception type
         value : exception value
         """
         return ListTB.structured_traceback(self, etype, value)
 
     def show_exception_only(self, etype, evalue):
         """Only print the exception type and message, without a traceback.
 
         Parameters
         ----------
         etype : exception type
         evalue : exception value
         """
         # This method needs to use __call__ from *this* class, not the one from
         # a subclass whose signature or behavior may be different
         ostream = self.ostream
         ostream.flush()
         ostream.write('\n'.join(self.get_exception_only(etype, evalue)))
         ostream.flush()
 
     def _some_str(self, value):
         # Lifted from traceback.py
         try:
             return py3compat.cast_unicode(str(value))
         except:
             return u'<unprintable %s object>' % type(value).__name__
 
 
 class FrameInfo:
     """
     Mirror of stack data's FrameInfo, but so that we can bypass highlighting on
     really long frames.
     """
 
     description: Optional[str]
     filename: Optional[str]
     lineno: Tuple[int]
     # number of context lines to use
     context: Optional[int]
 
     @classmethod
     def _from_stack_data_FrameInfo(cls, frame_info):
         return cls(
             getattr(frame_info, "description", None),
             getattr(frame_info, "filename", None),  # type: ignore[arg-type]
             getattr(frame_info, "lineno", None),  # type: ignore[arg-type]
             getattr(frame_info, "frame", None),
             getattr(frame_info, "code", None),
             sd=frame_info,
             context=None,
         )
 
     def __init__(
         self,
         description: Optional[str],
         filename: str,
         lineno: Tuple[int],
         frame,
         code,
         *,
         sd=None,
         context=None,
     ):
         self.description = description
         self.filename = filename
         self.lineno = lineno
         self.frame = frame
         self.code = code
         self._sd = sd
         self.context = context
 
         # self.lines = []
         if sd is None:
             ix = inspect.getsourcelines(frame)
             self.raw_lines = ix[0]
 
     @property
     def variables_in_executing_piece(self):
         if self._sd:
             return self._sd.variables_in_executing_piece
         else:
             return []
 
     @property
     def lines(self):
         return self._sd.lines
 
     @property
     def executing(self):
         if self._sd:
             return self._sd.executing
         else:
             return None
 
 
 # ----------------------------------------------------------------------------
 class VerboseTB(TBTools):
     """A port of Ka-Ping Yee's cgitb.py module that outputs color text instead
     of HTML.  Requires inspect and pydoc.  Crazy, man.
 
     Modified version which optionally strips the topmost entries from the
     traceback, to be used with alternate interpreters (because their own code
     would appear in the traceback)."""
 
     _tb_highlight = "bg:ansiyellow"
 
     def __init__(
         self,
         color_scheme: str = "Linux",
         call_pdb: bool = False,
         ostream=None,
         tb_offset: int = 0,
         long_header: bool = False,
         include_vars: bool = True,
         check_cache=None,
         debugger_cls=None,
         parent=None,
         config=None,
     ):
         """Specify traceback offset, headers and color scheme.
 
         Define how many frames to drop from the tracebacks. Calling it with
         tb_offset=1 allows use of this handler in interpreters which will have
         their own code at the top of the traceback (VerboseTB will first
         remove that frame before printing the traceback info)."""
         TBTools.__init__(
             self,
             color_scheme=color_scheme,
             call_pdb=call_pdb,
             ostream=ostream,
             parent=parent,
             config=config,
             debugger_cls=debugger_cls,
         )
         self.tb_offset = tb_offset
         self.long_header = long_header
         self.include_vars = include_vars
         # By default we use linecache.checkcache, but the user can provide a
         # different check_cache implementation.  This was formerly used by the
         # IPython kernel for interactive code, but is no longer necessary.
         if check_cache is None:
             check_cache = linecache.checkcache
         self.check_cache = check_cache
 
         self.skip_hidden = True
 
     def format_record(self, frame_info: FrameInfo):
         """Format a single stack frame"""
         assert isinstance(frame_info, FrameInfo)
         Colors = self.Colors  # just a shorthand + quicker name lookup
         ColorsNormal = Colors.Normal  # used a lot
 
         if isinstance(frame_info._sd, stack_data.RepeatedFrames):
             return '    %s[... skipping similar frames: %s]%s\n' % (
                 Colors.excName, frame_info.description, ColorsNormal)
 
         indent = " " * INDENT_SIZE
         em_normal = "%s\n%s%s" % (Colors.valEm, indent, ColorsNormal)
         tpl_call = f"in {Colors.vName}{{file}}{Colors.valEm}{{scope}}{ColorsNormal}"
         tpl_call_fail = "in %s%%s%s(***failed resolving arguments***)%s" % (
             Colors.vName,
             Colors.valEm,
             ColorsNormal,
         )
         tpl_name_val = "%%s %s= %%s%s" % (Colors.valEm, ColorsNormal)
 
         link = _format_filename(
             frame_info.filename,
             Colors.filenameEm,
             ColorsNormal,
             lineno=frame_info.lineno,
         )
         args, varargs, varkw, locals_ = inspect.getargvalues(frame_info.frame)
         if frame_info.executing is not None:
             func = frame_info.executing.code_qualname()
         else:
             func = "?"
         if func == "<module>":
             call = ""
         else:
             # Decide whether to include variable details or not
             var_repr = eqrepr if self.include_vars else nullrepr
             try:
                 scope = inspect.formatargvalues(
                     args, varargs, varkw, locals_, formatvalue=var_repr
                 )
                 call = tpl_call.format(file=func, scope=scope)
             except KeyError:
                 # This happens in situations like errors inside generator
                 # expressions, where local variables are listed in the
                 # line, but can't be extracted from the frame.  I'm not
                 # 100% sure this isn't actually a bug in inspect itself,
                 # but since there's no info for us to compute with, the
                 # best we can do is report the failure and move on.  Here
                 # we must *not* call any traceback construction again,
                 # because that would mess up use of %debug later on.  So we
                 # simply report the failure and move on.  The only
                 # limitation will be that this frame won't have locals
                 # listed in the call signature.  Quite subtle problem...
                 # I can't think of a good way to validate this in a unit
                 # test, but running a script consisting of:
                 #  dict( (k,v.strip()) for (k,v) in range(10) )
                 # will illustrate the error, if this exception catch is
                 # disabled.
                 call = tpl_call_fail % func
 
         lvals = ''
         lvals_list = []
         if self.include_vars:
             try:
                 # we likely want to fix stackdata at some point, but
                 # still need a workaround.
                 fibp = frame_info.variables_in_executing_piece
                 for var in fibp:
                     lvals_list.append(tpl_name_val % (var.name, repr(var.value)))
             except Exception:
                 lvals_list.append(
                     "Exception trying to inspect frame. No more locals available."
                 )
         if lvals_list:
             lvals = '%s%s' % (indent, em_normal.join(lvals_list))
 
         result = f'{link}{", " if call else ""}{call}\n'
         if frame_info._sd is None:
             # fast fallback if file is too long
             tpl_link = "%s%%s%s" % (Colors.filenameEm, ColorsNormal)
             link = tpl_link % util_path.compress_user(frame_info.filename)
             level = "%s %s\n" % (link, call)
             _line_format = PyColorize.Parser(
                 style=self.color_scheme_table.active_scheme_name, parent=self
             ).format2
             first_line = frame_info.code.co_firstlineno
             current_line = frame_info.lineno[0]
             raw_lines = frame_info.raw_lines
             index = current_line - first_line
 
             if index >= frame_info.context:
                 start = max(index - frame_info.context, 0)
                 stop = index + frame_info.context
                 index = frame_info.context
             else:
                 start = 0
                 stop = index + frame_info.context
             raw_lines = raw_lines[start:stop]
 
             return "%s%s" % (
                 level,
                 "".join(
                     _simple_format_traceback_lines(
                         current_line,
                         index,
                         raw_lines,
                         Colors,
                         lvals,
                         _line_format,
                     )
                 ),
             )
             # result += "\n".join(frame_info.raw_lines)
         else:
             result += "".join(
                 _format_traceback_lines(
                     frame_info.lines, Colors, self.has_colors, lvals
                 )
             )
         return result
 
     def prepare_header(self, etype: str, long_version: bool = False):
         colors = self.Colors  # just a shorthand + quicker name lookup
         colorsnormal = colors.Normal  # used a lot
         exc = '%s%s%s' % (colors.excName, etype, colorsnormal)
         width = min(75, get_terminal_size()[0])
         if long_version:
             # Header with the exception type, python version, and date
             pyver = 'Python ' + sys.version.split()[0] + ': ' + sys.executable
             date = time.ctime(time.time())
 
             head = "%s%s%s\n%s%s%s\n%s" % (
                 colors.topline,
                 "-" * width,
                 colorsnormal,
                 exc,
                 " " * (width - len(etype) - len(pyver)),
                 pyver,
                 date.rjust(width),
             )
             head += (
                 "\nA problem occurred executing Python code.  Here is the sequence of function"
                 "\ncalls leading up to the error, with the most recent (innermost) call last."
             )
         else:
             # Simplified header
             head = "%s%s" % (
                 exc,
                 "Traceback (most recent call last)".rjust(width - len(etype)),
             )
 
         return head
 
     def format_exception(self, etype, evalue):
         colors = self.Colors  # just a shorthand + quicker name lookup
         colorsnormal = colors.Normal  # used a lot
         # Get (safely) a string form of the exception info
         try:
             etype_str, evalue_str = map(str, (etype, evalue))
         except:
             # User exception is improperly defined.
             etype, evalue = str, sys.exc_info()[:2]
             etype_str, evalue_str = map(str, (etype, evalue))
+
+        # PEP-678 notes
+        notes = getattr(evalue, "__notes__", [])
+        if not isinstance(notes, Sequence) or isinstance(notes, (str, bytes)):
+            notes = [_safe_string(notes, "__notes__", func=repr)]
+
         # ... and format it
-        return ['%s%s%s: %s' % (colors.excName, etype_str,
-                                colorsnormal, py3compat.cast_unicode(evalue_str))]
+        return [
+            "{}{}{}: {}".format(
+                colors.excName,
+                etype_str,
+                colorsnormal,
+                py3compat.cast_unicode(evalue_str),
+            ),
+            *(
+                "{}{}".format(
+                    colorsnormal, _safe_string(py3compat.cast_unicode(n), "note")
+                )
+                for n in notes
+            ),
+        ]
 
     def format_exception_as_a_whole(
         self,
         etype: type,
         evalue: Optional[BaseException],
         etb: Optional[TracebackType],
         number_of_lines_of_context,
         tb_offset: Optional[int],
     ):
         """Formats the header, traceback and exception message for a single exception.
 
         This may be called multiple times by Python 3 exception chaining
         (PEP 3134).
         """
         # some locals
         orig_etype = etype
         try:
             etype = etype.__name__  # type: ignore
         except AttributeError:
             pass
 
         tb_offset = self.tb_offset if tb_offset is None else tb_offset
         assert isinstance(tb_offset, int)
         head = self.prepare_header(str(etype), self.long_header)
         records = (
             self.get_records(etb, number_of_lines_of_context, tb_offset) if etb else []
         )
 
         frames = []
         skipped = 0
         lastrecord = len(records) - 1
         for i, record in enumerate(records):
             if (
                 not isinstance(record._sd, stack_data.RepeatedFrames)
                 and self.skip_hidden
             ):
                 if (
                     record.frame.f_locals.get("__tracebackhide__", 0)
                     and i != lastrecord
                 ):
                     skipped += 1
                     continue
             if skipped:
                 Colors = self.Colors  # just a shorthand + quicker name lookup
                 ColorsNormal = Colors.Normal  # used a lot
                 frames.append(
                     "    %s[... skipping hidden %s frame]%s\n"
                     % (Colors.excName, skipped, ColorsNormal)
                 )
                 skipped = 0
             frames.append(self.format_record(record))
         if skipped:
             Colors = self.Colors  # just a shorthand + quicker name lookup
             ColorsNormal = Colors.Normal  # used a lot
             frames.append(
                 "    %s[... skipping hidden %s frame]%s\n"
                 % (Colors.excName, skipped, ColorsNormal)
             )
 
         formatted_exception = self.format_exception(etype, evalue)
         if records:
             frame_info = records[-1]
             ipinst = get_ipython()
             if ipinst is not None:
                 ipinst.hooks.synchronize_with_editor(frame_info.filename, frame_info.lineno, 0)
 
-        return [[head] + frames + [''.join(formatted_exception[0])]]
+        return [[head] + frames + formatted_exception]
 
     def get_records(
         self, etb: TracebackType, number_of_lines_of_context: int, tb_offset: int
     ):
         assert etb is not None
         context = number_of_lines_of_context - 1
         after = context // 2
         before = context - after
         if self.has_colors:
             style = get_style_by_name("default")
             style = stack_data.style_with_executing_node(style, self._tb_highlight)
             formatter = Terminal256Formatter(style=style)
         else:
             formatter = None
         options = stack_data.Options(
             before=before,
             after=after,
             pygments_formatter=formatter,
         )
 
         # Let's estimate the amount of code we will have to parse/highlight.
         cf: Optional[TracebackType] = etb
         max_len = 0
         tbs = []
         while cf is not None:
             try:
                 mod = inspect.getmodule(cf.tb_frame)
                 if mod is not None:
                     mod_name = mod.__name__
                     root_name, *_ = mod_name.split(".")
                     if root_name == "IPython":
                         cf = cf.tb_next
                         continue
                 max_len = get_line_number_of_frame(cf.tb_frame)
 
             except OSError:
                 max_len = 0
             max_len = max(max_len, max_len)
             tbs.append(cf)
             cf = getattr(cf, "tb_next", None)
 
         if max_len > FAST_THRESHOLD:
             FIs = []
             for tb in tbs:
                 frame = tb.tb_frame  # type: ignore
                 lineno = (frame.f_lineno,)
                 code = frame.f_code
                 filename = code.co_filename
                 # TODO: Here we need to use before/after/
                 FIs.append(
                     FrameInfo(
                         "Raw frame", filename, lineno, frame, code, context=context
                     )
                 )
             return FIs
         res = list(stack_data.FrameInfo.stack_data(etb, options=options))[tb_offset:]
         res = [FrameInfo._from_stack_data_FrameInfo(r) for r in res]
         return res
 
     def structured_traceback(
         self,
         etype: type,
         evalue: Optional[BaseException],
         etb: Optional[TracebackType] = None,
         tb_offset: Optional[int] = None,
         number_of_lines_of_context: int = 5,
     ):
         """Return a nice text document describing the traceback."""
         formatted_exception = self.format_exception_as_a_whole(etype, evalue, etb, number_of_lines_of_context,
                                                                tb_offset)
 
         colors = self.Colors  # just a shorthand + quicker name lookup
         colorsnormal = colors.Normal  # used a lot
         head = '%s%s%s' % (colors.topline, '-' * min(75, get_terminal_size()[0]), colorsnormal)
         structured_traceback_parts = [head]
         chained_exceptions_tb_offset = 0
         lines_of_context = 3
         formatted_exceptions = formatted_exception
         exception = self.get_parts_of_chained_exception(evalue)
         if exception:
             assert evalue is not None
             formatted_exceptions += self.prepare_chained_exception_message(evalue.__cause__)
             etype, evalue, etb = exception
         else:
             evalue = None
         chained_exc_ids = set()
         while evalue:
             formatted_exceptions += self.format_exception_as_a_whole(etype, evalue, etb, lines_of_context,
                                                                      chained_exceptions_tb_offset)
             exception = self.get_parts_of_chained_exception(evalue)
 
             if exception and not id(exception[1]) in chained_exc_ids:
                 chained_exc_ids.add(id(exception[1])) # trace exception to avoid infinite 'cause' loop
                 formatted_exceptions += self.prepare_chained_exception_message(evalue.__cause__)
                 etype, evalue, etb = exception
             else:
                 evalue = None
 
         # we want to see exceptions in a reversed order:
         # the first exception should be on top
         for formatted_exception in reversed(formatted_exceptions):
             structured_traceback_parts += formatted_exception
 
         return structured_traceback_parts
 
     def debugger(self, force: bool = False):
         """Call up the pdb debugger if desired, always clean up the tb
         reference.
 
         Keywords:
 
           - force(False): by default, this routine checks the instance call_pdb
             flag and does not actually invoke the debugger if the flag is false.
             The 'force' option forces the debugger to activate even if the flag
             is false.
 
         If the call_pdb flag is set, the pdb interactive debugger is
         invoked. In all cases, the self.tb reference to the current traceback
         is deleted to prevent lingering references which hamper memory
         management.
 
         Note that each call to pdb() does an 'import readline', so if your app
         requires a special setup for the readline completers, you'll have to
         fix that by hand after invoking the exception handler."""
 
         if force or self.call_pdb:
             if self.pdb is None:
                 self.pdb = self.debugger_cls()
             # the system displayhook may have changed, restore the original
             # for pdb
             display_trap = DisplayTrap(hook=sys.__displayhook__)
             with display_trap:
                 self.pdb.reset()
                 # Find the right frame so we don't pop up inside ipython itself
                 if hasattr(self, "tb") and self.tb is not None:  # type: ignore[has-type]
                     etb = self.tb  # type: ignore[has-type]
                 else:
                     etb = self.tb = sys.last_traceback
                 while self.tb is not None and self.tb.tb_next is not None:
                     assert self.tb.tb_next is not None
                     self.tb = self.tb.tb_next
                 if etb and etb.tb_next:
                     etb = etb.tb_next
                 self.pdb.botframe = etb.tb_frame
                 self.pdb.interaction(None, etb)
 
         if hasattr(self, 'tb'):
             del self.tb
 
     def handler(self, info=None):
         (etype, evalue, etb) = info or sys.exc_info()
         self.tb = etb
         ostream = self.ostream
         ostream.flush()
         ostream.write(self.text(etype, evalue, etb))
         ostream.write('\n')
         ostream.flush()
 
     # Changed so an instance can just be called as VerboseTB_inst() and print
     # out the right info on its own.
     def __call__(self, etype=None, evalue=None, etb=None):
         """This hook can replace sys.excepthook (for Python 2.1 or higher)."""
         if etb is None:
             self.handler()
         else:
             self.handler((etype, evalue, etb))
         try:
             self.debugger()
         except KeyboardInterrupt:
             print("\nKeyboardInterrupt")
 
 
 #----------------------------------------------------------------------------
 class FormattedTB(VerboseTB, ListTB):
     """Subclass ListTB but allow calling with a traceback.
 
     It can thus be used as a sys.excepthook for Python > 2.1.
 
     Also adds 'Context' and 'Verbose' modes, not available in ListTB.
 
     Allows a tb_offset to be specified. This is useful for situations where
     one needs to remove a number of topmost frames from the traceback (such as
     occurs with python programs that themselves execute other python code,
     like Python shells).  """
 
     mode: str
 
     def __init__(self, mode='Plain', color_scheme='Linux', call_pdb=False,
                  ostream=None,
                  tb_offset=0, long_header=False, include_vars=False,
                  check_cache=None, debugger_cls=None,
                  parent=None, config=None):
 
         # NEVER change the order of this list. Put new modes at the end:
         self.valid_modes = ['Plain', 'Context', 'Verbose', 'Minimal']
         self.verbose_modes = self.valid_modes[1:3]
 
         VerboseTB.__init__(self, color_scheme=color_scheme, call_pdb=call_pdb,
                            ostream=ostream, tb_offset=tb_offset,
                            long_header=long_header, include_vars=include_vars,
                            check_cache=check_cache, debugger_cls=debugger_cls,
                            parent=parent, config=config)
 
         # Different types of tracebacks are joined with different separators to
         # form a single string.  They are taken from this dict
         self._join_chars = dict(Plain='', Context='\n', Verbose='\n',
                                 Minimal='')
         # set_mode also sets the tb_join_char attribute
         self.set_mode(mode)
 
     def structured_traceback(self, etype, value, tb, tb_offset=None, number_of_lines_of_context=5):
         tb_offset = self.tb_offset if tb_offset is None else tb_offset
         mode = self.mode
         if mode in self.verbose_modes:
             # Verbose modes need a full traceback
             return VerboseTB.structured_traceback(
                 self, etype, value, tb, tb_offset, number_of_lines_of_context
             )
         elif mode == 'Minimal':
             return ListTB.get_exception_only(self, etype, value)
         else:
             # We must check the source cache because otherwise we can print
             # out-of-date source code.
             self.check_cache()
             # Now we can extract and format the exception
             return ListTB.structured_traceback(
                 self, etype, value, tb, tb_offset, number_of_lines_of_context
             )
 
     def stb2text(self, stb):
         """Convert a structured traceback (a list) to a string."""
         return self.tb_join_char.join(stb)
 
     def set_mode(self, mode: Optional[str] = None):
         """Switch to the desired mode.
 
         If mode is not specified, cycles through the available modes."""
 
         if not mode:
             new_idx = (self.valid_modes.index(self.mode) + 1 ) % \
                       len(self.valid_modes)
             self.mode = self.valid_modes[new_idx]
         elif mode not in self.valid_modes:
             raise ValueError(
                 "Unrecognized mode in FormattedTB: <" + mode + ">\n"
                 "Valid modes: " + str(self.valid_modes)
             )
         else:
             assert isinstance(mode, str)
             self.mode = mode
         # include variable details only in 'Verbose' mode
         self.include_vars = (self.mode == self.valid_modes[2])
         # Set the join character for generating text tracebacks
         self.tb_join_char = self._join_chars[self.mode]
 
     # some convenient shortcuts
     def plain(self):
         self.set_mode(self.valid_modes[0])
 
     def context(self):
         self.set_mode(self.valid_modes[1])
 
     def verbose(self):
         self.set_mode(self.valid_modes[2])
 
     def minimal(self):
         self.set_mode(self.valid_modes[3])
 
 
 #----------------------------------------------------------------------------
 class AutoFormattedTB(FormattedTB):
     """A traceback printer which can be called on the fly.
 
     It will find out about exceptions by itself.
 
     A brief example::
 
         AutoTB = AutoFormattedTB(mode = 'Verbose',color_scheme='Linux')
         try:
           ...
         except:
           AutoTB()  # or AutoTB(out=logfile) where logfile is an open file object
     """
 
     def __call__(self, etype=None, evalue=None, etb=None,
                  out=None, tb_offset=None):
         """Print out a formatted exception traceback.
 
         Optional arguments:
           - out: an open file-like object to direct output to.
 
           - tb_offset: the number of frames to skip over in the stack, on a
           per-call basis (this overrides temporarily the instance's tb_offset
           given at initialization time."""
 
         if out is None:
             out = self.ostream
         out.flush()
         out.write(self.text(etype, evalue, etb, tb_offset))
         out.write('\n')
         out.flush()
         # FIXME: we should remove the auto pdb behavior from here and leave
         # that to the clients.
         try:
             self.debugger()
         except KeyboardInterrupt:
             print("\nKeyboardInterrupt")
 
     def structured_traceback(
         self,
         etype: type,
         evalue: Optional[BaseException],
         etb: Optional[TracebackType] = None,
         tb_offset: Optional[int] = None,
         number_of_lines_of_context: int = 5,
     ):
         # tb: TracebackType or tupleof tb types ?
         if etype is None:
             etype, evalue, etb = sys.exc_info()
         if isinstance(etb, tuple):
             # tb is a tuple if this is a chained exception.
             self.tb = etb[0]
         else:
             self.tb = etb
         return FormattedTB.structured_traceback(
             self, etype, evalue, etb, tb_offset, number_of_lines_of_context
         )
 
 
 #---------------------------------------------------------------------------
 
 # A simple class to preserve Nathan's original functionality.
 class ColorTB(FormattedTB):
     """Shorthand to initialize a FormattedTB in Linux colors mode."""
 
     def __init__(self, color_scheme='Linux', call_pdb=0, **kwargs):
         FormattedTB.__init__(self, color_scheme=color_scheme,
                              call_pdb=call_pdb, **kwargs)
 
 
 class SyntaxTB(ListTB):
     """Extension which holds some state: the last exception value"""
 
     def __init__(self, color_scheme='NoColor', parent=None, config=None):
         ListTB.__init__(self, color_scheme, parent=parent, config=config)
         self.last_syntax_error = None
 
     def __call__(self, etype, value, elist):
         self.last_syntax_error = value
 
         ListTB.__call__(self, etype, value, elist)
 
     def structured_traceback(self, etype, value, elist, tb_offset=None,
                              context=5):
         # If the source file has been edited, the line in the syntax error can
         # be wrong (retrieved from an outdated cache). This replaces it with
         # the current value.
         if isinstance(value, SyntaxError) \
                 and isinstance(value.filename, str) \
                 and isinstance(value.lineno, int):
             linecache.checkcache(value.filename)
             newtext = linecache.getline(value.filename, value.lineno)
             if newtext:
                 value.text = newtext
         self.last_syntax_error = value
         return super(SyntaxTB, self).structured_traceback(etype, value, elist,
                                                           tb_offset=tb_offset, context=context)
 
     def clear_err_state(self):
         """Return the current error state and clear it"""
         e = self.last_syntax_error
         self.last_syntax_error = None
         return e
 
     def stb2text(self, stb):
         """Convert a structured traceback (a list) to a string."""
         return ''.join(stb)
 
 
 # some internal-use functions
 def text_repr(value):
     """Hopefully pretty robust repr equivalent."""
     # this is pretty horrible but should always return *something*
     try:
         return pydoc.text.repr(value)  # type: ignore[call-arg]
     except KeyboardInterrupt:
         raise
     except:
         try:
             return repr(value)
         except KeyboardInterrupt:
             raise
         except:
             try:
                 # all still in an except block so we catch
                 # getattr raising
                 name = getattr(value, '__name__', None)
                 if name:
                     # ick, recursion
                     return text_repr(name)
                 klass = getattr(value, '__class__', None)
                 if klass:
                     return '%s instance' % text_repr(klass)
             except KeyboardInterrupt:
                 raise
             except:
                 return 'UNRECOVERABLE REPR FAILURE'
 
 
 def eqrepr(value, repr=text_repr):
     return '=%s' % repr(value)
 
 
 def nullrepr(value, repr=text_repr):
     return ''