code: def test_variableoffsetwindowindexer_not_dti():
      # GH 54379
      with pytest.raises(
          ValueError, match="index must be a DatetimeIndex."
      ):
          VariableOffsetWindowIndexer(
              index="foo", offset=BusinessDay(1)
          )
  
imports: import numpy
  import pytest
  from pandas import DataFrame, MultiIndex, Series, concat, date_range
  import pandas._testing
  from pandas.api.indexers import BaseIndexer, FixedForwardWindowIndexer
  from pandas.core.indexers.objects import ExpandingIndexer, FixedWindowIndexer, VariableOffsetWindowIndexer
  from pandas.tseries.offsets import BusinessDay
label_desc: Use image node_id 9 for calling a global function with example usage: test_variableoffsetwindowindexer_not_dti() without return types