code: def test_drop_constant_columns(df_constant_columns):
      """Test that executes drop_constant_columns function."""
      processed_df = df_constant_columns.drop_constant_columns()
      expected_col_list = [
          "Bell__Chart",
          "decorated-elephant",
          "cities",
      ]
      assert processed_df.columns.to_list() == expected_col_list
      data = {
          "Bell__Chart": [1.234_523_45, 2.456_234, 3.234_612_5] * 3,
          "decorated-elephant": [1, 2, 3] * 3,
          "cities": ["Cambridge", "Shanghai", "Basel"] * 3,
      }
      expected_df = pd.DataFrame(data)
      assert_frame_equal(processed_df, expected_df)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_drop_constant_columns(df_constant_columns) without return types