Returns
        -------
        priors: [(String, Prior))]

def prior_tuples(self):
        """
        Returns
        -------
        priors: [(String, Prior))]
        """
        return [prior for tuple_prior in self.tuple_prior_tuples for prior in
                tuple_prior[1].prior_tuples] + self.direct_prior_tuples + [prior for prior_model in
                                                                           self.prior_model_tuples
                                                                           for prior in
                                                                           prior_model[1].prior_tuples]