code: def test_one_node():
      test = nx.Graph()
      test.add_node("a")
  
      # The expected communities are:
      ground_truth = {frozenset(["a"])}
  
      communities = nx.community.label_propagation_communities(test)
      result = {frozenset(c) for c in communities}
      assert result == ground_truth
  
imports: from itertools import chain, combinations
  import pytest
  import networkx
label_desc: Use image node_id 3 for calling a global function with example usage: test_one_node() without return types