class_docstr: This class implements the :class:`torch_geometric.data.GraphStore`
  interface to act as a local graph store for distributed training.
code: def _get_edge_index(
      self, edge_attr: EdgeAttr
  ) -> Optional[EdgeTensorType]:
      return self._edge_index.get(self.key(edge_attr), None)
  
imports: import json
  import os.path
  from typing import Any, Dict, List, Optional, Tuple, Union
  import torch
  from torch import Tensor
  from torch_geometric.data import EdgeAttr, GraphStore
  from torch_geometric.typing import EdgeTensorType, EdgeType, NodeType
  from torch_geometric.utils import sort_edge_index
label_desc: Use image node_id 9 for calling the LocalGraphStore obj's underlying member method code with example usage: obj._get_edge_index(edge_attr) and returns: self