docs: public void unlock() {
          String queryString = new QueryStringBuilder().appendParam("fields", "lock").toString();
          URL url = FILE_URL_TEMPLATE.buildWithQuery(this.getAPI().getBaseURL(), queryString, this.getID());
          BoxAPIRequest request = new BoxAPIRequest(this.getAPI(), url, "PUT");
  
          JsonObject lockObject = new JsonObject();
          lockObject.add("lock", JsonObject.NULL);
  
          request.setBody(lockObject.toString());
          request.send();
      }