Adding support for type and instance checking for Abstract Base Classes and other class definitions that leverage metaclasses. Existing logic enforced that the passed in type or class reference was actually a type by check "if type(arg) is not type then raise". This does not allow for using asserting type/instance checks against ABCs, collections.* (lots of ABCs), etc. Added tests for abstract classes.

Checks that don't work:

import collections
from assertpy import assert_that

def test_mapping():
    data = { 'a': 'b'}
    assert_that(data).is_instance_of(collections.Mapping)

Functions affected:

• is_type_of
• is_instance_of

Tests added:

tests/test_class.py

Defined 3 new classes, with a base implemented as an ABC. Added assertion tests for is_type_of() and is_instance_of(). All tests pass.