code: def l2_loss(x, y):
      loss = x - y
      loss = mx.symbol.smooth_l1(loss, scalar=1.0)
      # loss = loss*loss
      loss = mx.symbol.mean(loss)
      return loss
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import mxnet
  import numpy
  from config import config
label_desc: Use image node_id 13 for calling a global function with example usage: l2_loss(x, y) and returns: loss