code: def forward(self, mol_graph):
      n_samples = mol_graph.batch_size
  
      mol_line_graph = line_graph(
          mol_graph, backtracking=False, shared=True
      )
  
      n_nodes = mol_graph.num_nodes()
      n_edges = mol_graph.num_edges()
  
      mol_graph = self.run(mol_graph, mol_line_graph)
  
      # TODO: replace with unbatch or readout
      g_repr = mean_nodes(mol_graph, "h")
  
      self.n_samples_total += n_samples
      self.n_nodes_total += n_nodes
      self.n_edges_total += n_edges
      self.n_passes += 1
  
      return g_repr
  
imports: import dgl
  import dgl.function
  import rdkit.Chem
  import torch
  import torch.nn
  import torch.nn.functional
  from dgl import line_graph, mean_nodes
  from .chemutils import get_mol
label_desc: Use image node_id 2 for calling the DGLMPN obj's underlying member method code with example usage: obj.forward(mol_graph) and returns: g_repr