How to use the dictdiffer._compat.MutableMapping function in dictdiffer

def test_collection_subclasses(self):
        class DictA(MutableMapping):

            def __init__(self, *args, **kwargs):
                self.__dict__.update(*args, **kwargs)

            def __setitem__(self, key, value):
                self.__dict__[key] = value

            def __getitem__(self, key):
                return self.__dict__[key]

            def __delitem__(self, key):
                del self.__dict__[key]

            def __iter__(self):
                return iter(self.__dict__)

def __setitem__(self, key, value):
                self.__dict__[key] = value

            def __getitem__(self, key):
                return self.__dict__[key]

            def __delitem__(self, key):
                del self.__dict__[key]

            def __iter__(self):
                return iter(self.__dict__)

            def __len__(self):
                return len(self.__dict__)

        class DictB(MutableMapping):

            def __init__(self, *args, **kwargs):
                self.__dict__.update(*args, **kwargs)

            def __setitem__(self, key, value):
                self.__dict__[key] = value

            def __getitem__(self, key):
                return self.__dict__[key]

            def __delitem__(self, key):
                del self.__dict__[key]

            def __iter__(self):
                return iter(self.__dict__)

"""Dictdiffer is a helper module to diff and patch dictionaries."""

from copy import deepcopy

from ._compat import (PY2, Iterable, MutableMapping, MutableSequence,
                      MutableSet, string_types, text_type)
from .utils import EPSILON, PathLimit, are_different, dot_lookup
from .version import __version__

(ADD, REMOVE, CHANGE) = (
    'add', 'remove', 'change')

__all__ = ('diff', 'patch', 'swap', 'revert', 'dot_lookup', '__version__')

DICT_TYPES = (MutableMapping, )
LIST_TYPES = (MutableSequence, )
SET_TYPES = (MutableSet, )

try:
    import numpy
    HAS_NUMPY = True
    LIST_TYPES += (numpy.ndarray, )
except ImportError:  # pragma: no cover
    HAS_NUMPY = False


def diff(first, second, node=None, ignore=None, path_limit=None, expand=False,
         tolerance=EPSILON, dot_notation=True):
    """Compare two dictionary/list/set objects, and returns a diff result.

    Return an iterator with differences between two objects. The diff items