@staticmethod
def _validate_models(input_models):
    if (not hasattr(input_models, '__len__')):
        raise ValueError('models have to be an array but {}'.format(type(input_models)))
    valid_models = []
    for model in input_models:
        if isinstance(model, Recommender):
            valid_models.append(model)
    return valid_models
@staticmethod
def _validate_models(input_models):
    if (not hasattr(input_models, '__len__')):
        raise ValueError('models have to be an array but {}'.format(type(input_models)))
    valid_models = []
    for model in input_models:
        if isinstance(model, Recommender):
            valid_models.append(model)
    return valid_models