This is the full set of data types supported by XML-RPC. Method calls
may also raise a special \exception{Fault} instance, used to signal
XML-RPC server errors, or \exception{ProtocolError} used to signal an
-error in the HTTP/HTTPS transport layer.
+error in the HTTP/HTTPS transport layer. Note that even though starting
+with Python 2.2 you can subclass builtin types, the xmlrpclib module
+currently does not marshal instances of such subclasses.
When passing strings, characters special to XML such as \samp{<},
\samp{>}, and \samp{\&} will be automatically escaped. However, it's