code: def test_time_rolling_cov(window):
      # DataFrame
      prolling = ts.drop("a", axis=1).rolling(window)
      drolling = dts.drop("a", axis=1).rolling(window)
      assert_eq(prolling.cov(), drolling.cov())
  
      # Series
      prolling = ts.b.rolling(window)
      drolling = dts.b.rolling(window)
      assert_eq(prolling.cov(), drolling.cov())
  
imports: from __future__ import annotations
  import contextlib
  import datetime
  import numpy
  import pandas
  import pytest
  import dask.dataframe
  from dask.dataframe._compat import PANDAS_GE_210
  from dask.dataframe.utils import assert_eq
label_desc: Use image node_id 18 for calling a global function with example usage: test_time_rolling_cov(window) without return types