code: def binary_xloss(logits, labels, ignore=None):
      
      logits, labels = flatten_binary_scores(logits, labels, ignore)
      loss = StableBCELoss()(logits, Variable(labels.float()))
      return loss
docs: Binary Cross entropy loss
        logits: [B, H, W] Variable, logits at each pixel (between -\infty and +\infty)
        labels: [B, H, W] Tensor, binary ground truth masks (0 or 1)
        ignore: void class id