def model_requires_scaling(model):
    """
    Given a :py:class:`anticipy.forecast_models.ForecastModel`
        return True if the function requires scaling a_x

    :param model: A get_model_<modeltype> function from
        :py:mod:`anticipy.model.periodic_models` or
        :py:mod:`anticipy.model.aperiodic_models`
    :type model: function
    :return: True if function is logistic or sigmoidal
    :rtype: bool
    """
    requires_scaling = model is not None and model.name in ['logistic',
        'sigmoid']
    return requires_scaling
