Require an argument to implement multiple mixins

[mitar]

I have a base class an a set of mixins we are using to combine when defining new classes. The issue is that it seems currently there is no way to define that an argument should inherit from a list of base classes, and not just one:

def fun(argument: [BaseClass, CanBeSampledMixin, DescriptionMixin]) -> None:
    ...

So this would be that argument has to have all of the listed classes somewhere in its inheritance chain. In some way, it is similar to Union, maybe an Intersection? ;-)

[emmatyping]

I believe this is a duplicate of #213.

[mitar]

True! I literally named it the same. :-)