length, and N = batch size*. The logarithmized probabilities
        of the outputs (e.g. obtained with
        "torch.nn.functional.log_softmax()").
  * **targets** (*Tensor*) -- (N, S) or *(sum(target_lengths))*.
    Targets cannot be blank. In the second form, the targets are
    assumed to be concatenated.

  * **input_lengths** (*Tensor*) -- (N) or (). Lengths of the
    inputs (must each be \leq T)

  * **target_lengths** (*Tensor*) -- (N) or (). Lengths of the
    targets

  * **blank** (*int**, **optional*) -- Blank label. Default 0.

  * **reduction** (*str**, **optional*) -- Specifies the reduction
    to apply to the output: "'none'" | "'mean'" | "'sum'".
    "'none'": no reduction will be applied, "'mean'": the output
    losses will be divided by the target lengths and then the mean
    over the batch is taken, "'sum'": the output will be summed.
    Default: "'mean'"
