code: def test_fill_null_static_schema_4843() -> None:
      df1 = pl.DataFrame(
          {
              "a": [1, 2, None],
              "b": [1, None, 4],
          }
      ).lazy()
  
      df2 = df1.select([pl.col(pl.Int64).fill_null(0)])
      df3 = df2.select(pl.col(pl.Int64))
      assert df3.schema == {"a": pl.Int64, "b": pl.Int64}
  
imports: from __future__ import annotations
  from collections import OrderedDict
  from datetime import date, timedelta
  from typing import Any, Iterator, Mapping
  import pytest
  import polars
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 16 for calling a global function with example usage: test_fill_null_static_schema_4843() without return types