code: def forward(self, graph):
      if self.virtual_node:
          graph.virtual_node = self.v0.expand(
              [graph.num_graph, self.v0.shape[-1]]
          )
      g = self.main(graph)
      if self.conv_type == "gin+":
          g.node_feat["atom_feat"] = g.node_feat["atom_feat"][0]
  
      g.node_feat["atom_feat"] = self.appnp(g, g.node_feat["atom_feat"])
  
      return self.aggregate(g)
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  import pgl
  import pgl.nn
  from pgl.nn import functional
  from mol_encoder import AtomEncoder, BondEncoder
label_desc: Use image node_id 2 for calling the ClassifierNetwork obj's underlying member method code with example usage: obj.forward(graph) and returns: self