code: def test_eulerian_circuit_digraph(self):
      G = nx.DiGraph()
      nx.add_cycle(G, [0, 1, 2, 3])
  
      edges = list(nx.eulerian_circuit(G, source=0))
      nodes = [u for u, v in edges]
      assert nodes == [0, 1, 2, 3]
      assert edges == [(0, 1), (1, 2), (2, 3), (3, 0)]
  
      edges = list(nx.eulerian_circuit(G, source=1))
      nodes = [u for u, v in edges]
      assert nodes == [1, 2, 3, 0]
      assert edges == [(1, 2), (2, 3), (3, 0), (0, 1)]
  
imports: import collections
  import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestEulerianCircuit obj's underlying member method code with example usage: obj.test_eulerian_circuit_digraph() without return types