code: def test_unicode(self):
      corpus = (
          "Cat emoticons. \U0001F638 \U0001F639 \U0001F63A \U0001F63B"
      )
      token_counts = collections.Counter(corpus.split(" "))
  
      encoder = text_encoder.SubwordTextEncoder.build_to_target_size(
          100, token_counts, 2, 10
      )
  
      self.assertIn("\U0001F638", encoder._alphabet)
      self.assertIn("\U0001F63B", encoder.all_subtoken_strings)
  
imports: import collections
  import io
  import os
  import random
  import shutil
  import string
  import mock
  from six.moves import range
  import tensorflow.compat.v1
  from trax.data import text_encoder
label_desc: Use image node_id 3 for calling the SubwordTextEncoderTest obj's underlying member method code with example usage: obj.test_unicode() without return types