code: def test_query_4438() -> None:
      df = pl.DataFrame(
          {"x": [1, 2, 3, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 1, 1]}
      )
  
      q = (
          df.lazy()
          .with_columns(
              pl.col("x")
              .rolling_max(window_size=3)
              .alias("rolling_max")
          )
          .fill_null(strategy="backward")
          .with_columns(
              pl.col("rolling_max")
              .rolling_max(window_size=3)
              .alias("rolling_max_2")
          )
      )
      assert q.collect()["rolling_max_2"].to_list() == [
          None,
          None,
          3,
          10,
          10,
          10,
          10,
          10,
          9,
          8,
          7,
          6,
          5,
          4,
          3,
      ]
  
imports: from __future__ import annotations
  from datetime import datetime, timedelta
  from typing import Any
  import numpy
  import pandas
  import polars
  from polars.testing import assert_frame_equal
label_desc: Use image node_id 15 for calling a global function with example usage: test_query_4438() without return types