n <code class="code">s</code> after position <code class="code">i</code> or <code class="code"><span class="constructor">None</span></code> if <code class="code">c</code> does not occur in <code class="code">s</code> after position <code class="code">i</code>.
    <code class="code"><span class="constructor">Bytes</span>.index_opt&nbsp;s&nbsp;c</code> is equivalent to <code class="code"><span class="constructor">Bytes</span>.index_from_opt&nbsp;s&nbsp;0&nbsp;c</code>.</p>

<p>Raise <code class="code"><span 