code: def __init__(self, gamma, ignore_lb=255, *args, **kwargs):
      super(SoftmaxFocalLoss, self).__init__()
      self.gamma = gamma
      self.nll = nn.NLLLoss(ignore_index=ignore_lb)
  
file_path: PaddleDetection/ppdet/modeling/losses/clrnet_loss.py
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from ppdet.core.workspace import register
  from ppdet.modeling.clrnet_utils import accuracy
  from ppdet.modeling.assigners.clrnet_assigner import assign
  from ppdet.modeling.losses.clrnet_line_iou_loss import liou_loss
label_desc: Use image node_id 1 to create a new SoftmaxFocalLoss object from inherited base classes: nn with example: obj = SoftmaxFocalLoss(gamma, ignore_lb)