code: def test_getitem(self):
      with assertions.assertRaises(NotImplementedError):
          self.av[:1]
  
imports: import unittest
  import numpy
  import pytest
  import torch
  from pfrl import action_value
  from pfrl.testing import torch_assert_allclose
label_desc: Use image node_id 7 for calling the TestSingleActionValue obj's underlying member method code with example usage: obj.test_getitem() without return types