code: def test_hamiltonian_empty_graph():
      path = hamiltonian_path(DiGraph())
      assert len(path) == 0
  
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 11 for calling a global function with example usage: test_hamiltonian_empty_graph() without return types