(input/optional)
           A pointer to a CSSM_TUPLEGROUP containing a group of
           certificates, in TUPLE form. The tuple-certificates define
           the delegation of authorizations from the BaseAuthorizations
           to the Requestors.  If no additional authorization-granting
           tuples are provided, then this value is NULL and the
           BaseAuthorizations are the only source of trusted
           authorizations used as input to the authorization computation.