def configure_update(self, ns, definition):
        """
        Register an update endpoint.

        The definition's func should be an update function, which must:
        - accept kwargs for the request and path data
        - return an updated item

        :param ns: the namespace
        :param definition: the endpoint definition

        """
        @self.add_route(ns.instance_path, Operation.Update, ns)
        @request(definition.request_schema)
        @response(definition.response_schema)
        @wraps(definition.func)
        def update(**path_data):
            headers = dict()
            # NB: using partial here means that marshmallow will not validate required fields
            request_data = load_request_data(definition.request_schema, partial=True)
            response_data = require_response_data(definition.func(**merge_data(path_data, request_data)))
            definition.header_func(headers, response_data)
            response_format = self.negotiate_response_content(definition.response_formats)
            return dump_response_data(
                definition.response_schema,
                response_data,
                headers=headers,
                response_format=response_format,
            )

        update.__doc__ = "Update some or all of a {} by id".format(ns.subject_name)
Register an update endpoint.

        The definition's func should be an update function, which must:
        - accept kwargs for the request and path data
        - return an updated item

        :param ns: the namespace
        :param definition: the endpoint definition