\end{cases}
Note:
 When delta is set to 1, this loss is equivalent to
 "SmoothL1Loss". In general, this loss differs from "SmoothL1Loss"
 by a factor of delta (AKA beta in Smooth L1). See "SmoothL1Loss"
 for additional discussion on the differences in behavior between
 the two losses.

Parameters:
      * 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. Default: "'mean'"
  * **delta** (*float**, **optional*) -- Specifies the threshold
    at which to change between delta-scaled L1 and L2 loss. The
    value must be positive.  Default: 1.0

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