rindex_from&nbsp;s&nbsp;i&nbsp;c</code> returns 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;(<span class="constructor">Bytes</span>.length&nbsp;s&nbsp;-&nbsp;1)&nbsp;c</code>.</p>

<p>Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if <code class="code">i+1</