code: def test_when_splitter_splits_then_underlying_data_is_not_copied():
      splitter = ExpandingWindowSplitter(
          prediction_length=3, num_val_windows=2
      )
      original_df = DUMMY_VARIABLE_LENGTH_TS_DATAFRAME.copy()
      for train_fold, val_fold in splitter.split(original_df):
          assert train_fold._is_view
          assert (
              val_fold._is_view
              or val_fold.values.data == original_df.values.data
          )
  
file_path: autogluon/timeseries/tests/unittests/test_splitter.py
imports: import pytest
  from autogluon.timeseries.splitter import ExpandingWindowSplitter
  from .common import DATAFRAME_WITH_COVARIATES, DATAFRAME_WITH_STATIC, DUMMY_VARIABLE_LENGTH_TS_DATAFRAME
label_desc: Use image node_id 2 for calling a global function with example usage: test_when_splitter_splits_then_underlying_data_is_not_copied() without return types