code: def test_get_text_field_mask_returns_mask_key(self):
      text_field_tensors = {
          "tokens": torch.LongTensor(
              [[3, 4, 5, 0, 0], [1, 2, 0, 0, 0]]
          ),
          "mask": torch.LongTensor([[0, 0, 1]]),
      }
      assert_almost_equal(
          util.get_text_field_mask(text_field_tensors).numpy(),
          [[0, 0, 1]],
      )
  
imports: from __future__ import with_statement
  from __future__ import division
  from __future__ import absolute_import
  import numpy
  from numpy.testing import assert_array_almost_equal, assert_almost_equal
  import torch
  import pytest
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.nn import util
label_desc: Use image node_id 14 for calling the TestNnUtil obj's underlying member method code with example usage: obj.test_get_text_field_mask_returns_mask_key() without return types