class_docstr: Laplacian loss is refer to
  https://github.com/JizhiziLi/AIM/blob/master/core/evaluate.py#L83
class_docstr_tok: ["Laplacian","loss","is","refer","to","https",":","\/\/github.com\/JizhiziLi\/AIM\/blob\/master\/core\/evaluate.py","#","L83"]
code: def forward(self, logit, label, mask=None):
      if len(label.shape) == 3:
          label = label.unsqueeze(1)
      if mask is not None:
          if len(mask.shape) == 3:
              mask = mask.unsqueeze(1)
          logit = logit * mask
          label = label * mask
      pyr_label = self.laplacian_pyramid(label, self.gauss_kernel, 5)
      pyr_logit = self.laplacian_pyramid(logit, self.gauss_kernel, 5)
      loss = sum(F.l1_loss(a, b) for a, b in zip(pyr_label, pyr_logit))
  
      return loss
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.cvlibs import manager
  import cv2
label_desc: Use image node_id 2 for calling the LaplacianLoss obj's underlying member method code with example usage: obj.forward(logit, label, mask) and returns: loss