code: def test_rolling_time_series_split_empty():
      """Tests rolling_time_series_split when there is not enough data to create user splits"""
      tscv = RollingTimeSeriesSplit(
          forecast_horizon=50,
          min_train_periods=160,
          expanding_window=True,
          periods_between_splits=4,
          periods_between_train_test=0,
          max_splits=None,
      )
  
      with pytest.warns(Warning) as record:
          X = np.random.rand(200, 4)
          expected = [
              (
                  np.arange(180),
                  np.arange(start=180, stop=200),
              ),  # 90/10 split
          ]
          assert tscv.get_n_splits(X=X) == 1
          assert_splits_equal(tscv.split(X=X), expected)
          obtained_messages = "--".join(
              [r.message.args[0] for r in record]
          )
          assert (
              "There are no CV splits under the requested settings"
              in obtained_messages
          )
  
      with pytest.warns(Warning) as record:
          X = np.random.rand(150, 4)
          expected = [
              (
                  np.arange(135),
                  np.arange(start=135, stop=150),
              ),  # 90/10 split
          ]
          assert tscv.get_n_splits(X=X) == 1
          assert_splits_equal(tscv.split(X=X), expected)
          obtained_messages = "--".join(
              [r.message.args[0] for r in record]
          )
          assert (
              "There are no CV splits under the requested settings"
              in obtained_messages
          )
  
file_path: greykite/greykite/tests/sklearn/test_cross_validation.py
imports: import numpy
  import pytest
  from greykite.sklearn.cross_validation import RollingTimeSeriesSplit
label_desc: Use image node_id 5 for calling a global function with example usage: test_rolling_time_series_split_empty() without return types