def cohorts(institute_id, case_name):
    """Add/remove institute tags."""
    institute_obj, case_obj = institute_and_case(store, institute_id, case_name)
    user_obj = store.user(current_user.email)
    link = url_for('.case', institute_id=institute_id, case_name=case_name)
    cohort_tag = request.form['cohort_tag']
    if request.args.get('remove') == 'yes':
        store.remove_cohort(institute_obj, case_obj, user_obj, link, cohort_tag)
    else:
        store.add_cohort(institute_obj, case_obj, user_obj, link, cohort_tag)
    return redirect(request.referrer)
Add/remove institute tags.