code: public FutureAPIResponse unsetItemAsFuture(String iid, List<String> properties,
        DateTime eventTime) throws IOException {
      if (properties.isEmpty()) {
        throw new IllegalStateException("property list cannot be empty");
      }
      // converts the list into a map (to empty string) before creating the event object
      Map<String, Object> propertiesMap = Maps.newHashMap();
      for (String property : properties) {
        propertiesMap.put(property, "");
      }
      return createEventAsFuture(new Event()
          .event("$unset")
          .entityType("item")
          .entityId(iid)
          .eventTime(eventTime)
          .properties(propertiesMap));
    }
docs: Sends an unset item properties request. 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