code: def test_when_splitter_splits_then_cached_freq_is_preserved():
      splitter = ExpandingWindowSplitter(
          prediction_length=3, num_val_windows=2
      )
      for train_fold, val_fold in splitter.split(
          DUMMY_VARIABLE_LENGTH_TS_DATAFRAME
      ):
          assert (
              DUMMY_VARIABLE_LENGTH_TS_DATAFRAME._cached_freq
              == train_fold._cached_freq
              == val_fold._cached_freq
          )
  
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 1 for calling a global function with example usage: test_when_splitter_splits_then_cached_freq_is_preserved() without return types