code: def purge_tokens(self, input_token_attrs=None):
          
          if input_token_attrs is None:
              remove_attrs = self.token_attrs
          else:
              remove_attrs = [token_attr for token_attr in self.token_attrs if token_attr.token in input_token_attrs]
  
          self.token_attrs = [token_attr for token_attr in self.token_attrs if token_attr not in remove_attrs]
docs: Removes all specified token_attrs that exist in instance.token_attrs
          
          :param token_attrs: list(str), list of string values of tokens to remove.  If None, removes all