Loads the neighbors of the node from the igraph `Graph` instance that is
        wrapped by the graph that has this node.

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)