def __is_the_base_context_manager_class(cls):
    """
        Return whether `cls` is `ContextManager`.
        
        It's an ugly method, but unfortunately it's necessary because at one
        point we want to test if a class is `ContextManager` before
        `ContextManager` is defined in this module.
        """
    return (cls.__name__ == 'ContextManager' and cls.__module__ ==
        'python_toolbox.context_management.context_manager' and cls.mro() ==
        [cls, object])
