Note that the mimetypes.MimeTypes class was added in Python 2.2.

Doc/lib/libmimetypes.tex

@@ -113,6 +113,8 @@ want more than one MIME-type database:
 
   The optional \var{filenames} parameter can be used to cause
   additional files to be loaded ``on top'' of the default database.
+
+  \versionadded{2.2}
 \end{classdesc}