eturns the index of the last occurrence of
    byte <code class="code">c</code> in <code class="code">s</code> before position <code class="code">i+1</code>.  <code class="code">rindex&nbsp;s&nbsp;c</code> is equivalent
    to <code class="code">rindex_from&nbsp;s&nbsp;(length&nbsp;s&nbsp;-&nbsp;1)&nbsp;c</code>.</p>
</div>
<ul class="info-attributes">
<li><b>Raises</b><ul><li><code>Invalid_argument</code> if <code class="code">i+1</code> is not a valid position in <code class="code">s</code>.</li>
<li><cod