code: private void setValueAtPosition(int pos, ByteArraySegment value) {
          Preconditions.checkElementIndex(pos, getCount(), "pos must be non-negative and smaller than the number of items.");
          Preconditions.checkArgument(value.getLength() == this.config.valueLength, "Given value has incorrect length.");
          this.data.copyFrom(value, pos * this.config.entryLength + this.config.keyLength, value.getLength());
      }
docs: Sets the Value at the given position.
  
  @param pos   The Position to set the value at.
  @param value A ByteArraySegment representing the value to set.