code: int removeDisposedChildSlot(Slot slot) {
  		if (!slot.isReleased() || !subSlots.remove(slot)) {
  			throw new IllegalArgumentException();
  		}
  		return subSlots.size();
  	}
docs: Removes the given slot from this shared slot. This method Should only be called
  through this shared slot's {@link SlotSharingGroupAssignment}
  
  @param slot slot to be removed from the set of sub slots.
  @return Number of remaining sub slots