code: def test_fit_transform_datetime_15mins_idx_numeric_output(
      df_datetime_15mins_idx,
  ):
      """Tests that we get the expected outputs."""
      transformer = TimeSince(
          start=None,
          to_numeric=True,
          keep_original_columns=False,
          positive_only=False,
      )
  
      Xt = transformer.fit_transform(df_datetime_15mins_idx)
  
      expected = pd.DataFrame(
          data={"time_since_2000-01-01 00:00:00": [0, 15, 30, 45, 60]},
          index=df_datetime_15mins_idx.index,
      )
      assert_frame_equal(Xt, expected)
  
imports: import pandas
  import pytest
  from pandas.testing import assert_frame_equal
  from sktime.transformations.series.time_since import TimeSince
  from sktime.utils._testing.hierarchical import _make_hierarchical
label_desc: Use image node_id 8 for calling a global function with example usage: test_fit_transform_datetime_15mins_idx_numeric_output(df_datetime_15mins_idx) without return types