code: def prior_tuples(self):
          
          return {prior_tuple.prior: prior_tuple
                  for name, prior_model in self.prior_model_tuples
                  for prior_tuple in prior_model.prior_tuples}.values()
docs: Returns
          -------
          prior_tuple_dict: [(Prior, PriorTuple)]
              The set of all priors associated with this mapper