code: def test_concat_str_with_non_utf8_col() -> None:
      out = (
          pl.LazyFrame({"a": [0], "b": ["x"]})
          .select(
              pl.concat_str(["a", "b"], separator="-").fill_null(
                  pl.col("a")
              )
          )
          .collect()
      )
      expected = pl.Series("a", ["0-x"], dtype=pl.String)
      assert_series_equal(out.to_series(), expected)
  
imports: from __future__ import annotations
  from datetime import date, datetime
  from typing import TYPE_CHECKING
  import pytest
  import polars
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 26 for calling a global function with example usage: test_concat_str_with_non_utf8_col() without return types