</p></li>
</ul><ul><li><p><code>x + y</code> combines <code>x</code> and <code>y</code> into a new deque by appending <code>y</code>
to <code>x</code>.</p></li>
</ul><ul><li><p><code>x - y</code> element-wise removes all items of <code>y</code> from <code>x</code>, given
the element was contained in <code>x</code>.</p></li>
</ul><ul><li><p><code>addleft(.x, ...)</code> adds (possibly named) elements to left side of <code>.x</code>.</p></li>
<li><p><code>ref_addleft(.x, ...)</code> same as <code>addleft(.x, 