code: def test_triad_type():
      """Tests the triad_type function."""
      # 0 edges (1 type)
      G = nx.DiGraph({0: [], 1: [], 2: []})
      assert nx.triad_type(G) == "003"
      # 1 edge (1 type)
      G = nx.DiGraph({0: [1], 1: [], 2: []})
      assert nx.triad_type(G) == "012"
      # 2 edges (4 types)
      G = nx.DiGraph([(0, 1), (0, 2)])
      assert nx.triad_type(G) == "021D"
      G = nx.DiGraph({0: [1], 1: [0], 2: []})
      assert nx.triad_type(G) == "102"
      G = nx.DiGraph([(0, 1), (2, 1)])
      assert nx.triad_type(G) == "021U"
      G = nx.DiGraph([(0, 1), (1, 2)])
      assert nx.triad_type(G) == "021C"
      # 3 edges (4 types)
      G = nx.DiGraph([(0, 1), (1, 0), (2, 1)])
      assert nx.triad_type(G) == "111D"
      G = nx.DiGraph([(0, 1), (1, 0), (1, 2)])
      assert nx.triad_type(G) == "111U"
      G = nx.DiGraph([(0, 1), (1, 2), (0, 2)])
      assert nx.triad_type(G) == "030T"
      G = nx.DiGraph([(0, 1), (1, 2), (2, 0)])
      assert nx.triad_type(G) == "030C"
      # 4 edges (4 types)
      G = nx.DiGraph([(0, 1), (1, 0), (2, 0), (0, 2)])
      assert nx.triad_type(G) == "201"
      G = nx.DiGraph([(0, 1), (1, 0), (2, 0), (2, 1)])
      assert nx.triad_type(G) == "120D"
      G = nx.DiGraph([(0, 1), (1, 0), (0, 2), (1, 2)])
      assert nx.triad_type(G) == "120U"
      G = nx.DiGraph([(0, 1), (1, 0), (0, 2), (2, 1)])
      assert nx.triad_type(G) == "120C"
      # 5 edges (1 type)
      G = nx.DiGraph([(0, 1), (1, 0), (2, 1), (1, 2), (0, 2)])
      assert nx.triad_type(G) == "210"
      # 6 edges (1 type)
      G = nx.DiGraph([(0, 1), (1, 0), (1, 2), (2, 1), (0, 2), (2, 0)])
      assert nx.triad_type(G) == "300"
  
imports: import itertools
  from collections import defaultdict
  from random import sample
  import pytest
  import networkx
label_desc: Use image node_id 7 for calling a global function with example usage: test_triad_type() without return types