Why there's error for pycaret.containers.models.time_series.Basecdsdtforecaster? Curious about Basecdsdtforecaster.fit(y)-> what type for y?

Question

from pycaret.containers.models.time_series import BaseCdsDtForecaster
from sktime.transformations.series.summarize import WindowSummarizer
from sktime.regression.distance_based import KNeighborsTimeSeriesRegressor
from sktime.datasets import load_airline

y = load_airline()
KNN_DT = BaseCdsDtForecaster(fe_target_rr=[WindowSummarizer(lag_feature={'lag': [7, 6, 5,  4, 3, 2,1]},n_jobs=1)], 
regressor=KNeighborsTimeSeriesRegressor(n_jobs=-1, weights='distance'))

KNN_DT.fit(y) 

The error was:

TypeError: X is not of a supported input data type.X must be in a supported mtype format for Panel, found <class 'pandas.core.frame.DataFrame'>Use datatypes.check_is_mtype to check conformance with specifications.

Since the type of y is pd.Series and the index of y is set as 'period' type. I don't know what is the problem in the type.