code: def test_hide_header_elements() -> None:
      df = pl.DataFrame(
          {"a": [1, 2, 3], "b": [4, 5, 6], "c": [7, 8, 9]}
      )
  
      pl.Config.set_tbl_hide_column_data_types(True)
      assert (
          str(df) == "shape: (3, 3)\n"
          "┌───┬───┬───┐\n"
          "│ a ┆ b ┆ c │\n"
          "╞═══╪═══╪═══╡\n"
          "│ 1 ┆ 4 ┆ 7 │\n"
          "│ 2 ┆ 5 ┆ 8 │\n"
          "│ 3 ┆ 6 ┆ 9 │\n"
          "└───┴───┴───┘"
      )
  
      pl.Config.set_tbl_hide_column_data_types(
          False
      ).set_tbl_hide_column_names(True)
      assert (
          str(df) == "shape: (3, 3)\n"
          "┌─────┬─────┬─────┐\n"
          "│ i64 ┆ i64 ┆ i64 │\n"
          "╞═════╪═════╪═════╡\n"
          "│ 1   ┆ 4   ┆ 7   │\n"
          "│ 2   ┆ 5   ┆ 8   │\n"
          "│ 3   ┆ 6   ┆ 9   │\n"
          "└─────┴─────┴─────┘"
      )
  
imports: from __future__ import annotations
  import os
  from pathlib import Path
  from typing import Any, Iterator
  import pytest
  import polars
  import polars.polars
  from polars.config import _POLARS_CFG_ENV_VARS
label_desc: Use image node_id 3 for calling a global function with example usage: test_hide_header_elements() without return types