code: def testGetAllowedChars(self, word_counts, expected_chars):
      max_unique_chars = 5
      chars = learner.get_allowed_chars(word_counts, max_unique_chars)
      self.assertEqual(chars, expected_chars)
  
imports: import collections
  import logging
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.ops.ragged import ragged_string_ops
  from tensorflow_text.tools.wordpiece_vocab import wordpiece_tokenizer_learner_lib
label_desc: Use image node_id 1 for calling the GetAllowedCharsTest obj's underlying member method code with example usage: obj.testGetAllowedChars(word_counts, expected_chars) without return types