TypeError: 'NoneType' object is not callable while using async for

[Bobronium]

Executing first example from readme starts output files, but right after first iteration gives me this:

my_file_1.txt
my_other_file.jpeg
...
Traceback (most recent call last):
    ...
  File "/Users/rocky/dev/py/gdrive.py", line 12, in list_files
    async for page in full_res:
  File ".../aiogoogle/models.py", line 290, in _next_page_generator
    async with session_factory() as sess:
TypeError: 'NoneType' object is not callable

Additional info:
Due to some SSL issues, I used AiohttpSession with custom connector through session_factory
Just was able to run it without specifying any custom sessions, get same result

Possible reason:

aiogoogle/aiogoogle/sessions/aiohttp_session.py

Line 162 in c1f97ed

session_factory = self.__class__ if session_factory is None else None

Proposed solution:

Change line above to:

        session_factory = self.__class__ if session_factory is None else session_factory