def test_empty_queries(): t = IntervalTree() e = set() assert len(t) == 0 assert t.is_empty() assert t[3] == e assert t[4:6] == e assert t.begin() == 0 assert t.end() == 0 assert t[t.begin():t.end()] == e assert t.items() == e assert set(t) == e assert set(t.copy()) == e assert t.find_nested() == {} assert t.range().is_null() assert t.range().length() == 0 t.verify()