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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_or_create_vocab(self, data_dir, tmp_dir, force_get=False):
 """Get vocab for distill problems."""

    # We assume that vocab file is present in data_dir directory where the
    # data generated will be stored.
    vocab_filepath = os.path.join(data_dir, self.vocab_filename)
    encoder = text_encoder.SubwordTextEncoder(vocab_filepath)
    return encoder