Forgiving version of ``issubclass``

    Does not throw any exception when arguments are not of class type

def _forgiving_issubclass(derived_class, base_class):
    """Forgiving version of ``issubclass``

    Does not throw any exception when arguments are not of class type
    """
    return (type(derived_class) is ClassType and \
            type(base_class) is ClassType and \
            issubclass(derived_class, base_class))