code: def forward(self, x, edge_index, y, z):
      return self.propagate(edge_index, x=x, y=y, z=z)
  
imports: import random
  import pytest
  import torch
  from torch_geometric.data import HeteroData
  from torch_geometric.datasets import FakeHeteroDataset
  from torch_geometric.nn import GATConv, GCN2Conv, GCNConv, HeteroConv, Linear, MessagePassing, SAGEConv
  from torch_geometric.profile import benchmark
  from torch_geometric.testing import get_random_edge_index, onlyLinux, withCUDA, withPackage
label_desc: Use image node_id 2 for calling the CustomConv obj's underlying member method code with example usage: obj.forward(x, edge_index, y, z) and returns: self