code: def test_null_graph(self):
      G = nx.null_graph()
      ground_truth = set()
      self._check_communities(G, ground_truth)
  
imports: from itertools import chain, combinations
  import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestAsynLpaCommunities obj's underlying member method code with example usage: obj.test_null_graph() without return types