'List an IdP\'s supported protocols.
:param idp_id: ID of IdP object
:type idp_id: string
:raises keystone.exception.IdentityProviderNotFound: If the IdP
doesn\'t exist.
:returns: list of protocol ref
:rtype: list of dict'

@abc.abstractmethod
def list_protocols(self, idp_id):

    raise exception.NotImplemented()
