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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 to_json(self):
 """Serialize Vocab object to json string. This method does not serialize the underlying embedding. """

        if self._embedding:
            warnings.warn('Serialization of attached embedding '
                          'to json is not supported. '
                          'You may serialize the embedding to a binary format '
                          'separately using vocab.embedding.serialize')
        vocab_dict = {}
        vocab_dict['idx_to_token'] = self._idx_to_token
        vocab_dict['token_to_idx'] = dict(self._token_to_idx)
        vocab_dict['reserved_tokens'] = self._reserved_tokens
        vocab_dict['unknown_token'] = self._unknown_token
        vocab_dict['padding_token'] = self._padding_token
        vocab_dict['bos_token'] = self._bos_token
        vocab_dict['eos_token'] = self._eos_token
        return json.dumps(vocab_dict)