Not possible to subclass Requirements to add new methods

[sebbASF]

infrastructure-asfquart/src/asfquart/auth.py

Line 79 in a00d184

if not callable(req) or req != getattr(Requirements, req.__name__, None):

AFAICT, the above line means that only methods in the Requirements class are allowed.
So subclasses cannot be used to add a new method

[sebbASF]

Why is it even necessary to check where methods passed to require() are defined?
Surely all that matters is that they are callable (and ideally have the appropriate parameters)?