"size_average". When "reduce" is "False", returns a loss per
        batch element instead and ignores "size_average". Default:
        "True"
  * **reduction** (*str**, **optional*) -- Specifies the reduction
    to apply to the output: "'none'" | "'mean'" | "'sum'".
    "'none'": no reduction will be applied, "'mean'": the sum of
    the output will be divided by the number of elements in the
    output, "'sum'": the output will be summed. Note:
    "size_average" and "reduce" are in the process of being
    deprecated, and in the meantime, specifying either of those
    two args will override "reduction". Default: "'mean'"

Shape:
      * Input: (*), where * means any number of dimensions.
  * Target: (*), same shape as the input.

  * Output: scalar. If "reduction" is "'none'", then (*), same
    shape as input.
