Method enqueue

include/dmlc/thread_group.h:575–579

! * \brief Enqueue and item * \param item The item to enqueue */

   * \param item The item to enqueue
   */
  void enqueue(const ObjectType& item) {
    if (!shutdown_in_progress_) {
      queue_->enqueue(item);
    }
  }

  /*!
   * \brief Get the approximate size of the queue