code: def huber_loss(output, target):
      r"""See https://en.wikipedia.org/wiki/Huber_loss for definition.
  
      \delta is set to 1. This is not the right definition if output and target
      differ in more than one dimension.
      """
      a = target - output
      return C.reduce_sum(
          C.element_select(
              C.less(C.abs(a), 1), C.square(a) * 0.5, C.abs(a) - 0.5
          )
      )
  
label_desc: Use image node_id 1 for calling a global function with example usage: huber_loss(output, target) and returns: C