code: def _get_edge_index(
      self, edge_attr: EdgeAttr
  ) -> Optional[EdgeTensorType]:
      return self.store.get(self.key(edge_attr), None)
  
file_path: pytorch_geometric/torch_geometric/testing/graph_store.py
imports: from typing import Dict, List, Optional, Tuple
  from torch import Tensor
  from torch_geometric.data import EdgeAttr, GraphStore
  from torch_geometric.typing import EdgeTensorType
label_desc: Use image node_id 4 for calling the MyGraphStore obj's underlying member method code with example usage: obj._get_edge_index(edge_attr) and returns: self