distance to offset <code>i</code>. <code>n</code> must not be negative unless the
    collection conforms to the <code>BidirectionalCollection</code> protocol.
  <strong>limit:</strong> A valid index of the collection to use as a limit. If <code>n &gt; 0</code>,
    a limit that is less than <code>i</code> has no effect. Likewise, if <code>n &lt; 0</code>, a
    limit that is greater than <code>i</code> has no effect.
<strong>Returns:</strong> An index offset by <code>n</code> from the index <code>i</code>,