code: def all_neighbors(self):
      return set.union(set(self.edges.keys()), set(self.r_edges.keys()))
  
imports: from __future__ import annotations
  import heapq
  import itertools
  import math
  import random
  from river import base
label_desc: Use image node_id 18 for calling the Vertex obj's underlying member method code with example usage: obj.all_neighbors() and returns: set