class Singer {

    public synchronized void writeSchema(final String stream, final JsonObject schema, final JsonArray keys,
            final JsonArray bookmarks) {
        final JsonObject json = builderFactory
                .createObjectBuilder()
                .add("type", "SCHEMA")
                .add("stream", requireNonNull(stream, "stream can't be null"))
                .add("schema", schema)
                .add("key_properties", keys)
                .add("bookmark_properties", bookmarks)
                .build();
        runIo.getStdout().println(json);
    }

    public  Singer();

}