class_docstr: Abstract base strategy class.
  
  Implements attributes and operations shared by all strategies, including input and
  compatibility checks between passed estimator, data and task.
docstr: Validate input data.
docstr_tok: ["Validate","input","data","."]
code: def _validate_data(data):
      """Validate input data."""
      if not isinstance(data, pd.DataFrame):
          raise ValueError(
              f"Data must be pandas DataFrame, but found: {type(data)}"
          )
  
imports: import pandas
  from joblib import dump, load
  from sklearn.base import ClassifierMixin, RegressorMixin
  from sklearn.model_selection import GridSearchCV, RandomizedSearchCV
  from sklearn.pipeline import Pipeline
  from sktime.base import BaseEstimator
  from sktime.classification.base import BaseClassifier
  from sktime.forecasting.base._sktime import BaseForecaster
  from sktime.regression.base import BaseRegressor
label_desc: Use image node_id 8 for calling the BaseStrategy obj's underlying member method code with example usage: obj._validate_data(data) without return types