When developing a Python plug-in (in C++), how does one go about setting
the documentation for __new__?  In particular, given a new type
defined by a PyTypeObject structure in the C++, how does one document
the arguments which can be passed to the constructor.
Constructor arguments are usually documented in the type docstring, i.e. via the tp_doc slot, so you can do help(type) (or type? in IPython) instead of help(type.__new__) or help(type.__init__).
Generating constructor documentation for class defined in C++