get_protocol_members

Return the set of members defined in a Protocol.

Example::

    >>> from typing import Protocol, get_protocol_members
    >>> class P(Protocol):
    ...     def a(self) -> str: ...
    ...     b: int
    >>> get_protocol_members(P) == frozenset({'a', 'b'})
    True

Raise a TypeError for arguments that are not Protocols.