Set the identifier for the token
        @type this_id: string
        @param this_id: the identifier

def set_id(self,this_id):
        """
        Set the identifier for the token
        @type this_id: string
        @param this_id: the identifier
        """
        if self.type == 'NAF':
            return self.node.set('id',this_id)
        elif self.type == 'KAF':
            return self.node.set('wid',this_id)