code: function scrollToSelection(instance, selectionStartIndex, selectionEndIndex) {
      const lastSelectionIndexes = instance._lastSelectionIndexes
      if (
        selectionStartIndex !== -1 &&
        (selectionStartIndex !== lastSelectionIndexes.start || selectionEndIndex !== lastSelectionIndexes.end)
      ) {
        const changedIndex = selectionStartIndex !== lastSelectionIndexes.start ? selectionStartIndex : selectionEndIndex
        scrollToOption(instance, changedIndex)
      }
  
      lastSelectionIndexes.start = selectionStartIndex
      lastSelectionIndexes.end = selectionEndIndex
    }
docs: Scrolls, only if necessary, the UI of the provided szn-options element to make the last selected option visible.
  Which option is the last selected one is determined by comparing the provided index with the indexes passed to the
  previous call of this function.
  
  @param {SznElements.SznOptions} instance The szn-options element instance.
  @param {number} selectionStartIndex The index of the first selected option. The index must be a non-negative
  integer and cannot be greater that the total number of options; or set to <code>-1</code> if there is no
  option currently selected.
  @param {number} selectionEndIndex The index of the last selected option. The index must be a non-negative integer,
  cannot be greater than the total number of options and must not be lower than the
  <code>selectionStartIndex</code>; or set to <code>-1</code> if there is no option currently selected.