code: public String unsetItem(String iid, List<String> properties, DateTime eventTime)
        throws ExecutionException, InterruptedException, IOException {
      return createEvent(unsetItemAsFuture(iid, properties, eventTime));
    }
docs: Unsets properties of a item. The list must not be empty.
  
  @param iid ID of the item
  @param properties a list of all the properties to unset
  @param eventTime timestamp of the event
  @return ID of this event