code: def loss(self, pred, label):
      return F.nll_loss(pred, label)
  
file_path: deepsnap/examples/graph_classification/skip_models.py
imports: import torch
  import torch.nn
  import torch.nn.functional
  import torch_geometric.nn
  import torch_geometric.utils
label_desc: Use image node_id 4 for calling the SkipLastGNN obj's underlying member method code with example usage: obj.loss(pred, label) and returns: F