code: def test_index_converts_field_correctly(self):
      field = ProductionRuleField("S -> [NP, VP]", is_global_rule=True)
      field.index(self.vocab)
      assert field._rule_id == self.s_rule_index
  
file_path: magnitude/pymagnitude/third_party/allennlp/tests/data/fields/production_rule_field_test.py
imports: from __future__ import absolute_import
  from collections import defaultdict
  from numpy.testing import assert_almost_equal
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.data import Vocabulary
  from allennlp.data.fields import ListField, ProductionRuleField
label_desc: Use image node_id 3 for calling the TestProductionRuleField obj's underlying member method code with example usage: obj.test_index_converts_field_correctly() without return types