Update the HPO gene list for a case based on current terms.

def update_hpolist(self, case_obj):
        """Update the HPO gene list for a case based on current terms."""
        hpo_list = self.case_genelist(case_obj)
        hpo_results = hpo_genes(case_obj.phenotype_ids(),
                                *self.phenomizer_auth)

        if hpo_results is None:
            pass
            # Why raise here?
            # raise RuntimeError("couldn't link to genes, try again")
        else:
            gene_ids = [result['gene_id'] for result in hpo_results
                        if result['gene_id']]
            hpo_list.gene_ids = gene_ids
            self.save()