code: def test_zero_length():
      G = nx.cycle_graph(3)
      num_walks = nx.number_of_walks(G, 0)
      expected = {
          0: {0: 1, 1: 0, 2: 0},
          1: {0: 0, 1: 1, 2: 0},
          2: {0: 0, 1: 0, 2: 1},
      }
      assert num_walks == expected
  
file_path: networkx/networkx/algorithms/tests/test_walks.py
imports: import pytest
  import networkx
label_desc: Use image node_id 4 for calling a global function with example usage: test_zero_length() without return types