code: def test_irreducible1(self):
      # Graph taken from Figure 2 of
      # K. D. Cooper, T. J. Harvey, and K. Kennedy.
      # A simple, fast dominance algorithm.
      # Software Practice & Experience, 4:110, 2001.
      edges = [(1, 2), (2, 1), (3, 2), (4, 1), (5, 3), (5, 4)]
      G = nx.DiGraph(edges)
      assert nx.immediate_dominators(G, 5) == {
          i: 5 for i in range(1, 6)
      }
  
imports: import pytest
  import networkx
label_desc: Use image node_id 6 for calling the TestImmediateDominators obj's underlying member method code with example usage: obj.test_irreducible1() without return types