A list of list of states example -
        [[('x1', 'easy'), ('x2', 'hard')], [('x1', 'hard'), ('x2', 'medium')]]

        Returns
        -------
        True, if arg is a list of list of states else False.

def is_list_of_list_of_states(self, arg):
        """
        A list of list of states example -
        [[('x1', 'easy'), ('x2', 'hard')], [('x1', 'hard'), ('x2', 'medium')]]

        Returns
        -------
        True, if arg is a list of list of states else False.

        """
        if arg is None:
            return False
        return all([isinstance(arg, list),
                   all(isinstance(i, list) for i in arg),
                   all((isinstance(i, tuple) for i in lst) for lst in arg)])