[docs] [issue43739] Fixing the example code in Doc/extending/extending.rst to declare and initialize the pmodule variable to be of the right type.

Shreyan Avigyan <shreyan.avigyan@gmail.com> added the comment: I've signed the PSF CLA (as it is required) now. Please have a review. ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue43739> _______________________________________