gh-106318: Add examples for str.casefold() and str.lower() methods

Author: adorilson

Doc/library/stdtypes.rst

@@ -1841,7 +1841,14 @@ expression support in the :mod:`re` module).
    intended to remove all case distinctions in a string. For example, the German
    lowercase letter ``'ß'`` is equivalent to ``"ss"``. Since it is already
    lowercase, :meth:`lower` would do nothing to ``'ß'``; :meth:`casefold`
-   converts it to ``"ss"``.
+   converts it to ``"ss"``, as follows:
+
+   .. doctest::
+
+      >>> 'ß'.casefold()
+      'ss'
+      >>> 'ß'.lower()
+      'ß'
 
    The casefolding algorithm is `described in section 3.13.3 'Default Case
    Folding' of the Unicode Standard
@@ -2250,7 +2257,12 @@ expression support in the :mod:`re` module).
 .. method:: str.lower()
 
    Return a copy of the string with all the cased characters [4]_ converted to
-   lowercase.
+   lowercase. For example:
+
+   .. doctest::
+
+      >>> 'Lower Method Example'.lower()
+      'lower method example'
 
    The lowercasing algorithm used is `described in section 3.13.2 'Default Case
    Conversion' of the Unicode Standard