code: ByteArraySegment getKeyAt(int pos) {
          Preconditions.checkElementIndex(pos, getCount(), "pos must be non-negative and smaller than the number of items.");
          return this.data.subSegment(pos * this.config.entryLength, this.config.keyLength);
      }
docs: Gets the Key at the given Position.
  
  @param pos The Position to get the Key at.
  @return A ByteArraySegment containing the Key at the given Position. Note that this is a view inside a larger array
  and any modifications to that array will be reflected in this. If this value needs to be held for
  longer then it is recommended to get a copy of it (use getCopy()).