code: def get_edge(self, source: Node, target: Node) -> Optional[Edge]:
          
          return self.get_edge_by_index(source.index, target.index)
docs: Returns the edge connection the given nodes if such an edge exists.
  
          Arguments:
              source (Node): One of the endpoints of the queried edge.
              target (Node): The other endpoint of the queried edge.
  
          Returns:
              Returns the edge connection the given nodes
              or `None` if no such node exists.