src/transformers/models/gpt2/tokenization_gpt2.py/GPT2Tokenizer/_convert_token_to_id
class GPT2Tokenizer:    def _convert_token_to_id(self, token):
        """Converts a token (str) in an id using the vocab."""
        return self.encoder.get(token, self.encoder.get(self.unk_token))