code: func (f *DeltaFIFO) willObjectBeDeletedLocked(id string) bool {
  	deltas := f.items[id]
  	return len(deltas) > 0 && deltas[len(deltas)-1].Type == Deleted
  }
docs: // willObjectBeDeletedLocked returns true only if the last delta for the
  // given object is Delete. Caller must lock first.