code: def test_is_empty():
      assert StoryGraph([]).is_empty()
  
file_path: rasa/tests/shared/core/training_data/test_graph.py
imports: from rasa.shared.core.training_data.structures import StoryGraph
  import rasa.shared.core.training_data.loading
  from rasa.shared.core.domain import Domain
label_desc: Use image node_id 4 for calling a global function with example usage: test_is_empty() without return types