German example in casefolding is plain incorrect.

#Casefolding is similar to lowercasing but more aggressive because it is #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, lower() would do nothing to 'ß'; casefold() converts it to #"ss".

It is not true that "ß" is equivalent to "ss" and has not been since an orthography reform in 1996. These are to be used in distinct use cases. "ß" after a diphthong or a long/open vowel. "ss" after a short/closed vowel. The documentation correctly describes (in this case) how Python handles the .casefold() for this letter, although the behavior itself is incorrect.

As mentioned before, in 2017 an official upper-case version of "ß" has been introduced into German orthography: "ẞ". The German example should be stated as current incorrect behavior in the documentation.

+1 to adding previously mentioned sentence: In addition to lowercasing, this function also expands ligatures, for example, "fi" becomes "fi".