code: def test_empty_sequence():
      """Joining the empty sequence results in the tree with one node."""
      T = nx.join_trees([])
      assert len(T) == 1
      assert T.number_of_edges() == 0
  
file_path: networkx/networkx/algorithms/tree/tests/test_operations.py
imports: from itertools import chain
  import networkx
  from networkx.utils import edges_equal, nodes_equal
label_desc: Use image node_id 2 for calling a global function with example usage: test_empty_sequence() without return types