value that is ignored and does not contribute to the input
        gradient. When "size_average" is "True", the loss is averaged
        over non-ignored targets. Note that "ignore_index" is only
        applicable when the target contains class indices.
  * **reduce** (*bool**, **optional*) -- Deprecated (see
    "reduction"). By default, the losses are averaged or summed
    over observations for each minibatch depending on
    "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 weighted
    mean of the output is taken, "'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
