class_docstr: Head of GNN for node prediction.
code: def forward(self, batch):
      batch = self.layer_post_mp(batch)
      pred, label = self._apply_index(batch)
      return pred, label
  
imports: import torch.nn
  from torch_geometric.graphgym.register import register_head
label_desc: Use image node_id 3 for calling the ExampleNodeHead obj's underlying member method code with example usage: obj.forward(batch) and returns: pred,  label