code: def get_length_task_loss(config: LossConfig) -> 'Loss':
      
      if config.length_task_link is not None:
          if config.length_task_link == C.LINK_NORMAL:
              return MSELoss(config,
                             output_names=[C.LENRATIO_OUTPUT_NAME],
                             label_names=[C.LENRATIO_LABEL_NAME])
          elif config.length_task_link == C.LINK_POISSON:
              return PoissonLoss(config,
                                 output_names=[C.LENRATIO_OUTPUT_NAME],
                                 label_names=[C.LENRATIO_LABEL_NAME])
          else:
              raise ValueError("unknown link function name for length task: %s" % config.length_task_link)
      return None
docs: Returns a Loss instance.
  
      :param config: Loss configuration.
      :return: Instance implementing Loss.