mod_python is not able to invoke APR Optional Functions. There are
some cases however where this could be of great benifit.
For example, consider writing an authentication or authorization handler
which needs to determine SSL properties (even if to just answer the
simple question: is the connection SSL encrypted). The normal way of
looking in the subprocess_env for SSL_* variables does not work in those
early handler phases because those variables are not set until the fixup phase.
The mod_ssl module though does provide both a ssl_is_https() and
ssl_var_lookup() optional functions which can be used in earlier
phases. For example look at how mod_rewrite calls those; using
the APR_DECLARE_OPTIONAL_FN and APR_RETRIEVE_OPTIONAL_FN
I can see how it might be very hard to support optional functions in
general because of the C type linkage issue, but perhaps a select few
could be coded directly into mod_python.