code: def forward(self, det_loss, reid_loss):
      loss = (
          paddle.exp(-self.det_weight) * det_loss
          + paddle.exp(-self.reid_weight) * reid_loss
          + (self.det_weight + self.reid_weight)
      )
      loss *= 0.5
      return {"loss": loss}
  
file_path: PaddleDetection/ppdet/modeling/losses/fairmot_loss.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import paddle
  import paddle.nn
  from paddle.nn.initializer import Constant
  from ppdet.core.workspace import register
label_desc: Use image node_id 2 for calling the FairMOTLoss obj's underlying member method code with example usage: obj.forward(det_loss, reid_loss) and returns: dict