public void init(SiddhiAppContext siddhiAppContext) {
        // there's nothing to be done, since we moved the
        // type validation mechanism to the transport itself.
    }
Sink Callback is used to get {@link Event}s from Siddhi Streams using
{@link StreamJunction} and send them to {@link SinkMapper}s to do the mapping.
modules/siddhi-core/src/main/java/io/siddhi/core/stream/output/sink/SinkCallback.java