code: def compute_loss(self, preds, yb):
      return loss_fn(preds, yb)
  
imports: from icevision.imports import *
  from icevision.utils import *
  from icevision.metrics import *
  from icevision.engines.lightning.lightning_model_adapter import LightningModelAdapter
  from icevision.models.torchvision.loss_fn import loss_fn
  from icevision.core.record_components import InstanceMasksRecordComponent, BBoxesRecordComponent
  from icevision.core.mask import MaskArray
  from icevision.core.bbox import BBox
label_desc: Use image node_id 5 for calling the RCNNModelAdapter obj's underlying member method code with example usage: obj.compute_loss(preds, yb) and returns: loss_fn