我目前有关需求就是需要得到我每次写入之后的id，所以我用了conflux.subscribeEpochs
但是一直报错
Error: Subscriptions are not available on this transport.
at f. (js-conflux-sdk.umd.min.js:29)
at f (js-conflux-sdk.umd.min.js:27)
at Generator._invoke (js-conflux-sdk.umd.min.js:27)
at Generator.next (js-conflux-sdk.umd.min.js:27)
at n (js-conflux-sdk.umd.min.js:1)
at s (js-conflux-sdk.umd.min.js:1)
