@classmethod
def _validate_estimator_dict(cls, estimator_dict):
    """Validate ``estimator_dict`` in inputs for ``HyperparameterTuner.create()``"""
    if estimator_dict is None or len(estimator_dict) == 0:
        raise ValueError('At least one estimator should be provided')
    if None in estimator_dict.keys():
        raise ValueError('Estimator names cannot be None')
