Docs: replace 'definition header' with 'call signature'

IPython/core/debugger.py

@@ -477,7 +477,7 b' class Pdb(OldPdb):'
     do_l = do_list
 
     def do_pdef(self, arg):
-        """Print the definition header for any callable object.
+        """Print the call signature for any callable object.
 
         The debugger interface to %pdef"""
         namespaces = [('Locals', self.curframe.f_locals),

IPython/core/magics/namespace.py

@@ -69,7 +69,7 b' class NamespaceMagics(Magics):'
     @skip_doctest
     @line_magic
     def pdef(self, parameter_s='', namespaces=None):
-        """Print the definition header for any callable object.
+        """Print the call signature for any callable object.
 
         If the object is a class, print the constructor information.
 

IPython/core/oinspect.py

@@ -344,7 +344,7 b' class Inspector:'
         self.set_active_scheme(scheme)
 
     def _getdef(self,obj,oname=''):
-        """Return the definition header for any callable object.
+        """Return the call signature for any callable object.
 
         If any exception is generated, None is returned instead and the
         exception is suppressed."""
@@ -373,7 +373,7 b' class Inspector:'
             print()
 
     def pdef(self, obj, oname=''):
-        """Print the definition header for any callable object.
+        """Print the call signature for any callable object.
 
         If the object is a class, print the constructor information."""
 

docs/source/interactive/reference.txt

@@ -337,7 +337,7 b' this is just a summary:'
     * **%pdoc <object>**: Print (or run through a pager if too long) the
       docstring for an object. If the given object is a class, it will
       print both the class and the constructor docstrings.
-    * **%pdef <object>**: Print the definition header for any callable
+    * **%pdef <object>**: Print the call signature for any callable
       object. If the object is a class, print the constructor information.
     * **%psource <object>**: Print (or run through a pager if too long)
       the source code for an object.