code: def test_concat_diagonal(
      a: pl.DataFrame,
      b: pl.DataFrame,
      c: pl.DataFrame,
      strategy: ConcatMethod,
  ) -> None:
      for out in [
          pl.concat([a, b, c], how=strategy),
          pl.concat(
              [a.lazy(), b.lazy(), c.lazy()], how=strategy
          ).collect(),
      ]:
          expected = pl.DataFrame(
              {
                  "a": [1, 2, None, None, 5, 6],
                  "b": [None, None, "a", "b", "x", "y"],
                  "c": [None, None, 3, 4, 5, 6],
                  "d": [None, None, None, None, 5, 6],
              }
          )
          assert_frame_equal(out, expected)
  
imports: from __future__ import annotations
  from datetime import timedelta
  from typing import TYPE_CHECKING
  import numpy
  import pytest
  import polars
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 2 for calling a global function with example usage: test_concat_diagonal(a, b, c, strategy) without return types