code: def test_transform_panel(df_panel):
      """Test `.transform()` on panel data."""
      transformer = DateTimeFeatures(
          manual_selection=["year", "month_of_year", "day_of_month"],
          keep_original_columns=True,
      )
      Xt = transformer.fit_transform(df_panel)
  
      expected = pd.DataFrame(
          index=df_panel.index,
          data={
              "c0": df_panel["c0"].values,
              "year": [2000, 2000, 2000, 2000, 2000, 2000],
              "month_of_year": [1, 1, 1, 1, 1, 1],
              "day_of_month": [1, 2, 3, 1, 2, 3],
          },
      )
      assert_frame_equal(Xt, expected)
  
imports: import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
  from sktime.datasets import load_airline, load_longley, load_PBS_dataset
  from sktime.split import temporal_train_test_split
  from sktime.tests.test_switch import run_test_for_class
  from sktime.transformations.series.date import DateTimeFeatures
  from sktime.utils._testing.hierarchical import _make_hierarchical
label_desc: Use image node_id 25 for calling a global function with example usage: test_transform_panel(df_panel) without return types