code: def test_legal_actions(self):
      states = np.array([[0, 0, 0], [1, 0, 0], [2, 1, 0]])
      self.assertEqual(
          [(0, 0), (0, 1), (0, 2), (1, 1), (1, 2), (2, 2)],
          self.env._legal_actions(states),
      )
  
file_path: agents/tf_agents/environments/examples/tic_tac_toe_environment_test.py
imports: import numpy
  from tf_agents.environments import utils
  from tf_agents.environments.examples.tic_tac_toe_environment import TicTacToeEnvironment
  from tf_agents.trajectories.time_step import StepType
  from tf_agents.trajectories.time_step import TimeStep
  from tf_agents.utils import test_utils
label_desc: Use image node_id 4 for calling the TicTacToeEnvironmentTest obj's underlying member method code with example usage: obj.test_legal_actions() without return types