code: def forward(self, pred, gold, raw, col_names):
      return F.mse_loss(pred, gold)
  
imports: import os
  import paddle
  import paddle.nn
  import paddle.nn.functional
  import numpy
label_desc: Use image node_id 2 for calling the MSELoss obj's underlying member method code with example usage: obj.forward(pred, gold, raw, col_names) and returns: F