error. For ``DecodeFSDefault``, the return type is ``const char *``; return a ``NULL``
pointer to indicate an error.
-(There's also an experimental ``NoneType`` converter, which lets you
-return ``Py_None`` on success or ``NULL`` on failure, without having
-to increment the reference count on ``Py_None``. I'm not sure it adds
-enough clarity to be worth using.)
-
To see all the return converters Argument Clinic supports, along with
their parameters (if any),
just run ``Tools/clinic/clinic.py --converters`` for the full list.