3.3.0+ Crashes when assigning `__init__` rather than defining it

[Daverball]

If you do something like the following:

class Base:
    def __init__(self) -> None:
        pass


class SomeMixin:
    if TYPE_CHECKING:
        # forward declare __init__
        __init__ = Base.__init__  # type:ignore[assignment]

Autoapi will crash in the mapping step when trying to access overloads on the class node, this is presumably because the following check does not guard against non-method nodes:

sphinx-autoapi/autoapi/_objects.py

Lines 452 to 464 in b9b2a95

	if self.constructor:
	overload_data = self.constructor.obj["overloads"]
	autodoc_typehints = getattr(
	self.app.config, "autodoc_typehints", "signature"
	)
	show_annotations = autodoc_typehints not in ("none", "description")
	overloads = [
	(
	_format_args(args, show_annotations, ignore_self="self"),
	return_annotation,
	)
	for args, return_annotation in overload_data
	]

I couldn't really figure out why this didn't cause a crash prior to 3.3.0, but at the very least it should be fairly simple to avoid a crash here, by adding an additional guard. Doing something more sophisticated would require more work. But I don't think it is necessary, considering this is a really rare hacky workaround and in fact I no longer needed to use it in the places that caused the crash.

But it still can't hurt to avoid this crash in the future, since it was a pain to debug.