from trytond.transaction import Transaction
    pat_invoice = fields.Function(fields.Char('Paait time', help="How long the patient waited",states=STATES),'get_invoice')

    def get_invoice(self, name):
        pool = Pool()
        print(self.patient.name,"")
        cursor = Transaction().connection.cursor()
        cursor.execute("SELECT COUNT(id)  FROM gnuhealth_health_service WHERE patient = %s",(a))
        res = cursor.fetchone()[0]
        return(str(res))