presto-plugin-toolkit/src/main/java/io/prestosql/plugin/base/authentication/KerberosTicketUtils.java/KerberosTicketUtils/getTicketGrantingTicket
class KerberosTicketUtils:    public static KerberosTicket getTicketGrantingTicket(Subject subject)
    {
        Set<KerberosTicket> tickets = subject.getPrivateCredentials(KerberosTicket.class);
        for (KerberosTicket ticket : tickets) {
            if (isOriginalTicketGrantingTicket(ticket)) {
                return ticket;
            }
        }
        throw new IllegalArgumentException("kerberos ticket not found in " + subject);
    }