code: def mapper_from_partial_prior_arguments(self, arguments):
          
          original_prior_dict = {prior: prior for prior in self.priors}
          return self.mapper_from_prior_arguments({**original_prior_dict, **arguments})
docs: Creates a new model mapper from a dictionary mapping_matrix existing priors to new priors, keeping existing
          priors where no mapping is provided.
  
          Parameters
          ----------
          arguments: {Prior: Prior}
              A dictionary mapping_matrix priors to priors
  
          Returns
          -------
          model_mapper: ModelMapper
              A new model mapper with updated priors.