code: def normalize_example(self, task, example, encoder, hparams, is_infer):
      
      # Here we use the default function for NLP tasks that makes everything
      # a part of "targets" feature. Override in your subclasses for other uses.
      vocab_offset = encoder.vocab_size + len(self.task_list)
      return normalize_example_nlp(
          task, example, is_infer, self.vocab_type, vocab_offset,
          hparams.multiproblem_max_input_length,
          hparams.multiproblem_max_target_length,
          hparams.multiproblem_fixed_train_length)
docs: Normalize the examples from different tasks so they can be merged.