docs: def _load_neighbors_from_external_source(self) -> None:
          """
          Loads the neighbors of the node from the igraph `Graph` instance that is
          wrapped by the graph that has this node.
          """
          graph: IGraphWrapper = self._graph
          ig_vertex: IGraphVertex = graph.wrapped_graph.vs[self._igraph_index]
          ig_neighbors: List[IGraphVertex] = ig_vertex.neighbors()
          for ig_neighbor in ig_neighbors:
              try:
                  name: str = ig_neighbor["name"]
              except KeyError:
                  name: str = str(ig_neighbor.index)
  
              try:
                  external_id: Optional[str] = ig_neighbor["external_id"]
              except KeyError:
                  external_id: Optional[str] = None
  
              neighbor: IGraphNode = graph.nodes.get_node_by_name(name,
                                                                  can_validate_and_load=True,
                                                                  external_id=external_id)
              graph.add_edge(self, neighbor)