def parse_cache_control_header(value, on_update=None, cls=None):
    if cls is None:
        cls = RequestCacheControl
    if not value:
        return cls(None, on_update)
    return cls(parse_dict_header(value), on_update)
Method to verify if a particular role exists
dataset/ETHPy150Open Eforcers/gae-flask-todo/lib/werkzeug/http.py/parse_cache_control_header--crossover with--dataset/ETHPy150Open aws/aws-cli/awscli/customizations/datapipeline/createdefaultroles.py/CreateDefaultRoles._check_if_role_exists