code: def test_empty_union():
      # Tests if a null-union does nothing.
      uf = nx.utils.UnionFind((0, 1))
      uf.union()
      assert uf[0] == 0
      assert uf[1] == 1
  
imports: import networkx
label_desc: Use image node_id 5 for calling a global function with example usage: test_empty_union() without return types