code: @MustBeLocked (ELockType.WRITE)
    @Nullable
    protected final IMPLTYPE internalDeleteItem (@Nullable final String sID)
    {
      return internalDeleteItem (sID, true);
    }
docs: Delete the item by removing it from the map. If something was remove the
  onDeleteItem callback is invoked. Must only be invoked inside a write-lock.
  
  @param sID
  The ID to be removed. May be <code>null</code>.
  @return The deleted item. If <code>null</code> no such item was found and
  therefore nothing was removed.