def stem_tokens(self, tokens):
        """
        Stem each token of tokens

        Args:
          tokens: List of tokens to stem

        Returns:
          List of final stems
        """
        for i, token in enumerate(tokens):
            tokens[i] = self.stemmer(token)

        return tokens

        Stem each token of tokens

        Args:
          tokens: List of tokens to stem

        Returns:
          List of final stems
        
utils_nlp/eval/rouge/rouge_ext.py