deprecated, and in the meantime, specifying either of those
        two args will override "reduction". Default: "'mean'"
Shape:
      * Input: (N, C) where N is the batch size and C is the
        number of classes.
  * Target: (N, C), label targets padded by -1 ensuring same shape
    as the input.

  * Output: scalar. If "reduction" is "'none'", then (N).
