update formatter what's new

docs/source/whatsnew/pr/formatters.txt

@@ -1,19 +1,20
 DisplayFormatter changes
 ========================
 
 There was no official way to query or remove callbacks in the Formatter API.
 To remedy this, the following methods are added to :class:`BaseFormatter`:
 
 - ``lookup(instance)`` - return appropriate callback or a given object
 - ``lookup_by_type(type_or_str)`` - return appropriate callback for a given type or ``'mod.name'`` type string
-- ``pop(type_or_str)`` - remove an type (by type or string)
+- ``pop(type_or_str)`` - remove a type (by type or string).
+  Pass a second argument to avoid KeyError (like dict).
 
 All of the above methods raise a KeyError if no match is found.
 
 And the following methods are changed:
 
 - ``for_type(type_or_str)`` - behaves the same as before, only adding support for ``'mod.name'``
   type strings in addition to plain types. This removes the need for ``for_type_by_name()``,
   but it remains for backward compatibility.