two args will override "reduction". Default: "'mean'"
  * **pos_weight** (*Tensor**, **optional*) -- a weight of
    positive examples. Must be a vector with length equal to the
    number of classes.

Return type:
      Tensor
Examples:
  >>> input = torch.randn(3, requires_grad=True)
  >>> target = torch.empty(3).random_(2)
  >>> loss = F.binary_cross_entropy_with_logits(input, target)
  >>> loss.backward()
