code: func (w handledIters) markItersWithKeyAsHandled(startIdx int, key uint64) {
  	for i := startIdx; i < len(w); i++ {
  		wrapped := w[i]
  		currKey, _ := wrapped.iter.Value()
  		if currKey == key {
  			w[i].handled = true
  		}
  	}
  }
docs: // Check all the iters from startIdx and up to see whether their next
  // key is the given key; if it is, mark them as handled.