code: def forward(self, x, edge_index, edge_label_index):
      z = model.encode(x, edge_index)
      return model.decode(z, edge_label_index).view(-1)
  
file_path: pytorch_geometric/examples/explain/gnn_explainer_link_pred.py
imports: import os.path
  import torch
  import torch.nn.functional
  from sklearn.metrics import roc_auc_score
  import torch_geometric.transforms
  from torch_geometric.datasets import Planetoid
  from torch_geometric.explain import Explainer, GNNExplainer, ModelConfig
  from torch_geometric.nn import GCNConv
label_desc: Use image node_id 4 for calling the GCN obj's underlying member method code with example usage: obj.forward(x, edge_index, edge_label_index) and returns: model