code: def test_positive_tagging_should_handle_zero_length(self):
      # Given
      slot_name = "animal"
      slot_size = 0
  
      # When
      tags = []
      for scheme in TaggingScheme:
          tags.append(positive_tagging(scheme, slot_name, slot_size))
  
      # Then
      expected_tags = [[]] * len(TaggingScheme)
      self.assertEqual(tags, expected_tags)
  
imports: from __future__ import unicode_literals
  from builtins import range
  from mock import patch
  from snips_nlu.constants import LANGUAGE_EN
  from snips_nlu.preprocessing import Token, tokenize
  from snips_nlu.result import unresolved_slot
  from snips_nlu.slot_filler.crf_utils import BEGINNING_PREFIX, INSIDE_PREFIX, LAST_PREFIX, OUTSIDE, TaggingScheme, UNIT_PREFIX, end_of_bilou_slot, end_of_bio_slot, negative_tagging, positive_tagging, start_of_bilou_slot, start_of_bio_slot, tags_to_slots, utterance_to_sample
  from snips_nlu.tests.utils import SnipsTest
label_desc: Use image node_id 4 for calling the TestCRFUtils obj's underlying member method code with example usage: obj.test_positive_tagging_should_handle_zero_length() without return types