code: public static boolean isRegistered(@Nonnull Item item) {
          ItemDeletion instance = instance();
          if (instance == null) {
              return false;
          }
          instance.lock.readLock().lock();
          try {
              return instance.registrations.contains(item);
          } finally {
              instance.lock.readLock().unlock();
          }
      }
docs: Checks if the supplied {@link Item} is explicitly registered for deletion.
  
  @param item the item.
  @return {@code true} if and only if the supplied {@link Item} has been {@linkplain #register(Item)}ed for
  deletion.