code: def __init__(self, gamma=2, size_average=True):
      super(FocalLoss2d, self).__init__()
      self.gamma = gamma
      self.size_average = size_average
  
imports: import torch
  import torch.nn
  import torch.nn.functional
label_desc: Use image node_id 1 to create a new FocalLoss2d object from inherited base classes: nn with example: obj = FocalLoss2d(gamma, size_average)