code: def test_multilabel_field_empty_field_works(self):
      vocab = Vocabulary()
      vocab.add_token_to_namespace(
          "label1", namespace="test_empty_labels"
      )
      vocab.add_token_to_namespace(
          "label2", namespace="test_empty_labels"
      )
  
      f = MultiLabelField([], label_namespace="test_empty_labels")
      f.index(vocab)
      tensor = (
          f.as_tensor(f.get_padding_lengths()).detach().cpu().numpy()
      )
      numpy.testing.assert_array_almost_equal(
          tensor, numpy.array([0, 0])
      )
  
imports: from __future__ import with_statement
  from __future__ import absolute_import
  from __future__ import print_function
  import numpy
  import pytest
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.data.fields import MultiLabelField
  from allennlp.data.vocabulary import Vocabulary
label_desc: Use image node_id 8 for calling the TestMultiLabelField obj's underlying member method code with example usage: obj.test_multilabel_field_empty_field_works() without return types