code: def test_rolling_forward_skewness(frame_or_series, step):
      values = np.arange(10.0)
      values[5] = 100.0
  
      indexer = FixedForwardWindowIndexer(window_size=5)
      rolling = frame_or_series(values).rolling(
          window=indexer, min_periods=3, step=step
      )
      result = rolling.skew()
  
      expected = frame_or_series(
          [
              0.0,
              2.232396,
              2.229508,
              2.228340,
              2.229091,
              2.231989,
              0.0,
              0.0,
              np.nan,
              np.nan,
          ]
      )[::step]
      tm.assert_equal(result, expected)
  
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 6 for calling a global function with example usage: test_rolling_forward_skewness(frame_or_series, step) without return types