="code">extend&nbsp;s&nbsp;left&nbsp;right</code> returns a new byte sequence that contains
    the bytes of <code class="code">s</code>, with <code class="code">left</code> uninitialized bytes prepended and
    <code class="code">right</code> uninitialized bytes appended to it. If <code class="code">left</code> or <code class="code">right</code>
    is negative, then bytes are removed (instead of appended) from
    the corresponding side of <code class="code">s</code>.</p>

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