Attempt to remove backcall.

This was meant to allow this API to evolve, but I have the impression
was not use much.

This will reduce our dependencies and reliance on older packages.

IPython/core/events.py

@@ -13,8 +13,6 b' events and the arguments which will be passed to them.'
    This API is experimental in IPython 2.0, and may be revised in future versions.
 """
 
-from backcall import callback_prototype
-
 
 class EventManager(object):
     """Manage a collection of events and a sequence of callbacks for each.
@@ -63,23 +61,14 b' class EventManager(object):'
         """
         if not callable(function):
             raise TypeError('Need a callable, got %r' % function)
-        callback_proto = available_events.get(event)
         if function not in self.callbacks[event]:
-            self.callbacks[event].append(callback_proto.adapt(function))
+            self.callbacks[event].append(function)
     
     def unregister(self, event, function):
         """Remove a callback from the given event."""
         if function in self.callbacks[event]:
             return self.callbacks[event].remove(function)
 
-        # Remove callback in case ``function`` was adapted by `backcall`.
-        for callback in self.callbacks[event]:
-            try:
-                if callback.__wrapped__ is function:
-                    return self.callbacks[event].remove(callback)
-            except AttributeError:
-                pass
-
         raise ValueError('Function {!r} is not registered as a {} callback'.format(function, event))
 
     def trigger(self, event, *args, **kwargs):

setup.cfg

@@ -30,7 +30,6 b' python_requires = >=3.9'
 zip_safe = False
 install_requires =
     appnope; sys_platform == "darwin"
-    backcall
     colorama; sys_platform == "win32"
     decorator
     exceptiongroup; python_version<'3.11'