code: def backward_loss(z, backward_error):
      return t.sum(z * backward_error)
  
imports: import torch
  import torch
  from fate.arch import Context
  from fate.ml.nn.model_zoo.agg_layer.agg_layer import AggLayerGuest, AggLayerHost
  from fate.ml.nn.model_zoo.agg_layer.fedpass.agg_layer import FedPassAggLayerGuest, FedPassAggLayerHost, get_model
  from fate.ml.nn.model_zoo.agg_layer.sshe.agg_layer import SSHEAggLayerHost, SSHEAggLayerGuest
  from typing import Any, Dict, List, Union, Callable, Literal
  from dataclasses import dataclass, fields
  from enum import Enum
  import logging
  from torch import device
label_desc: Use image node_id 2 for calling a global function with example usage: backward_loss(z, backward_error) and returns: t