code: def test_reachable_pair():
      """Tests for a reachable pair of nodes."""
      G = DiGraph([(0, 1), (1, 2), (2, 0)])
      assert is_reachable(G, 0, 2)
  
imports: from itertools import combinations
  import pytest
  from networkx import DiGraph
  from networkx.algorithms.tournament import hamiltonian_path, index_satisfying, is_reachable, is_strongly_connected, is_tournament, random_tournament, score_sequence, tournament_matrix
label_desc: Use image node_id 17 for calling a global function with example usage: test_reachable_pair() without return types