Sets the opinion identifier
        @type my_id: string
        @param my_id: the opinion identifier

def set_id(self,my_id):
        """
        Sets the opinion identifier
        @type my_id: string
        @param my_id: the opinion identifier
        """
        if self.type == 'NAF':
            self.node.set('id',my_id)
        elif self.type == 'KAF':
            self.node.set('oid',my_id)