def _check_main_disease(self, cr, uid, ids, context=None):
        '''
            verify there's only one main disease 
        '''
        for r in self.browse(cr, uid, ids, context=context):
            diseases_ids = self.search(cr,uid,[('attentiont_id','=',r.attentiont_id.id),('diseases_type','=','main')])

            if len(diseases_ids) > 1:
                return False

        return True