code: def loss_fn(predictions, targets):
      return F.nll_loss(predictions, targets)
  
file_path: pytorch/functorch/notebooks/_src/plot_per_sample_gradients.py
imports: import torch
  import torch.nn
  import torch.nn.functional
  from functorch import grad, make_functional_with_buffers, vmap
label_desc: Use image node_id 1 for calling a global function with example usage: loss_fn(predictions, targets) and returns: F