code: def _check_windows(windows, allow_empty_window=False):
      assert isinstance(windows, list)
      for window in windows:
          assert isinstance(window, np.ndarray)
          assert np.issubdtype(window.dtype, np.integer)
          assert window.ndim == 1
          if not allow_empty_window:
              assert len(window) > 0
  
file_path: sktime/sktime/split/tests/test_split.py
imports: import numpy
  import pytest
  from sktime.forecasting.base import ForecastingHorizon
  from sktime.split import ExpandingWindowSplitter, SlidingWindowSplitter
  from sktime.utils.datetime import _coerce_duration_to_int
  from sktime.utils.validation import array_is_datetime64, array_is_int, array_is_timedelta_or_date_offset, is_int
  from sktime.utils.validation.forecasting import check_fh
label_desc: Use image node_id 2 for calling a global function with example usage: _check_windows(windows, allow_empty_window) without return types