code: def forward(self, x, edge_index):
      x = self.conv1(x, edge_index).relu()
      x = self.conv2(x, edge_index)
      x = self.conv3(x, edge_index)
      return x
  
file_path: pytorch_geometric/test/explain/algorithm/test_attention_explainer.py
imports: import pytest
  import torch
  from torch_geometric.explain import AttentionExplainer, Explainer
  from torch_geometric.explain.config import ExplanationType, MaskType
  from torch_geometric.nn import AttentiveFP, GATConv, GATv2Conv, TransformerConv
label_desc: Use image node_id 2 for calling the AttentionGNN obj's underlying member method code with example usage: obj.forward(x, edge_index) and returns: x