code: def edge_index(
      self, id1: str, id2: str, id3: Optional[str] = None
  ) -> np.ndarray:
      src = id1
      rel, dst = (id3, id2) if id3 is None else (id2, id3)
      rel = self.__rels__[(src, dst)] if rel is None else rel
      name = f"{src}___{rel}___{dst}"
      path = osp.join(self.dir, "processed", name, "edge_index.npy")
      return np.load(path)
  
imports: from typing import Optional, Union, Dict
  import os
  import shutil
  import os.path
  import torch
  import numpy
  from ogb.utils.url import decide_download, download_url, extract_zip, makedirs
  from ogb.lsc.utils import split_test
label_desc: Use image node_id 16 for calling the MAG240MDataset obj's underlying member method code with example usage: obj.edge_index(id1, id2, id3) and returns: np