add superclass note

Author: dg-pb

Doc/library/difflib.rst

@@ -43,6 +43,8 @@ diffs. For comparing directories and files, see the :mod:`filecmp` module.
 .. class:: SequenceMatcher
    :noindex:
 
+   Implementation of :class:`SequenceMatcherBase`.
+
    This is a flexible class for comparing pairs of sequences of any type, so long
    as the sequence elements are :term:`hashable`.  The basic algorithm predates, and is a
    little fancier than, an algorithm published in the late 1980's by Ratcliff and

Lib/difflib.py

@@ -468,6 +468,8 @@ def real_quick_ratio(self):
 class SequenceMatcher(SequenceMatcherBase):
 
     """
+    Implementation of SequenceMatcherBase.
+
     SequenceMatcher is a flexible class for comparing pairs of sequences of
     any type, so long as the sequence elements are hashable.  The basic
     algorithm predates, and is a little fancier than, an algorithm