final FutureData<DataSiftResult> future = new FutureData<>();
final ObjectMapper mapper = new ObjectMapper();
URI uri = newParams().forURL(config.newAPIEndpointURI(EXISTS));
try {
Request request = config.http()
.POST(uri, new PageReader(newRequestCallback(future, new BaseDataSiftResult(), config)))
.form("id", list.getId())
.form("items", mapper.writeValueAsString(items));
performRequest(future, request);
} catch (JsonProcessingException e) {
failNotify(future, e);