imprv: generate: Hint callbacks

[matperc]

~Blocked by this bug https://github.com/python/mypy/issues/15177~

Closes #144 Closes #149

[matperc]

The bug in mypy is fixed so it should work now.

@lovetox can you test on your code base if everything works fine?

[matperc]

~There is a problem on typing with Gio.AsyncReadyCallback it should take var args~

I've fixed this. It works now, I'll leave the draft status since it works only with mypy master.

[matperc]

With mypy 1.7 it's working. Before merge please check if it is working as expected in your codebase

[lovetox]

This generates for me invalid python, if i try it on Gtk3

xoptions=<flags GTK_EXPAND | GTK_FILL of type Gtk.AttachOptions>

also please make a second space between code and FIXME comment

: ... # FIXME Function -> : ... # FIXME Function

This reduces the work the formatter has to do

[lovetox]

oh it seems its not this MR that does this, i have this also on master

I added https://github.com/pygobject/pygobject-stubs/issues/169

[lovetox]

i tested this and didnt run into any problems with the MR.

[matperc]

also please make a second space between code and FIXME comment

: ... # FIXME Function -> : ... # FIXME Function

This reduces the work the formatter has to do

Is this related to this PR?