code: def test_hierarchical_singlewindowsplitter():
      """Test broadcasting of window splitters to hierarchical data.
  
      Also certifies for failure cas in bug #4972.
      """
      y = _make_hierarchical(hierarchy_levels=(2, 3), random_state=0)
      splitter = SingleWindowSplitter(fh=[1, 2], window_length=10)
      splits = list(splitter.split(y))
      assert len(splits) == 1, "Should only be one split"
  
file_path: sktime/sktime/split/base/tests/test_base.py
imports: import numpy
  import pandas
  import pytest
  from sktime.forecasting.tests._config import TEST_FHS, TEST_FHS_TIMEDELTA, TEST_STEP_LENGTHS, TEST_WINDOW_LENGTHS
  from sktime.split.base._common import _inputs_are_supported
  from sktime.split.expandingwindow import ExpandingWindowSplitter
  from sktime.split.singlewindow import SingleWindowSplitter
  from sktime.split.slidingwindow import SlidingWindowSplitter
  from sktime.utils._testing.hierarchical import _make_hierarchical
  from sktime.utils._testing.panel import _make_panel
  from sktime.utils._testing.series import _make_series
label_desc: Use image node_id 4 for calling a global function with example usage: test_hierarchical_singlewindowsplitter() without return types