ERR_MULTIPLE_CALLBACK

回调被多次调用。

【A callback was called more than once.】

回调几乎总是只应被调用一次，因为查询要么可以被完成，要么可以被拒绝，但不能同时发生。如果多次调用回调，则可能出现后者情况。

【A callback is almost always meant to only be called once as the query can either be fulfilled or rejected but not both at the same time. The latter would be possible by calling a callback more than once.】