def METHOD_NAME(empty_dag: DAG) -> None:
    """Test transitive reduction no reduction."""
    dag = empty_dag
    dag.from_dict({"a": ["b", "c"], "b": ["d"], "c": ["d"], "d": []})
    dag.transitive_reduction()
    assert dag.graph == {"a": {"b", "c"}, "b": {"d"}, "c": {"d"}, "d": set()}