code: def _truncate_seq_pair(self, tokens_a, tokens_b, max_length):
          
          # This is a simple heuristic which will always truncate the longer sequence
          # one token at a time. This makes more sense than truncating an equal percent
          # of tokens from each, since if one sequence is very short then each token
          # that's truncated likely contains more information than a longer sequence.
          while True:
              total_length = len(tokens_a) + len(tokens_b)
              if total_length <= max_length:
                  break
              if len(tokens_a) > len(tokens_b):
                  tokens_a.pop()
              else:
                  tokens_b.pop()
docs: Truncates a sequence pair in place to the maximum length.