docs: 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)])