how to add a custom type to unittest.TestCase.assertEqual

If you would like your TestCase class to understand one of your custom types as if it were standard, use addTypeEqualityFunc to supply a custom comparison function.

source: unittest/case.py:415

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def addTypeEqualityFunc(self, typeobj, function):
    """Add a type specific assertEqual style function to compare a type.
    This method is for use by TestCase subclasses that need to register
    their own type equality functions to provide nicer error messages.
    Args:
        typeobj: The data type to call this function on when both values
                are of the same type in assertEqual().
        function: The callable taking two arguments and an optional
                msg= argument that raises self.failureException with a
                useful error message when the two arguments are not equal.
    """
    self._type_equality_funcs[typeobj] = function