code: @MustBeLocked (ELockType.WRITE)
    protected final void internalUpdateItem (@Nonnull final IMPLTYPE aItem)
    {
      internalUpdateItem (aItem, true);
    }
docs: Update an existing item including invoking the callback. Must only be
  invoked inside a write-lock.
  
  @param aItem
  The item to be updated. May not be <code>null</code>.
  @throws IllegalArgumentException
  If no item with the same ID is already contained