Set of all subsets
<p>In Python2 I could use</p>

<pre><code>def subsets(mySet):
    return reduce(lambda z, x: z + [y + [x] for y in z], mySet, [[]])
</code></pre>

<p>to find all subsets of <code>mySet</code>. Python 3 has removed <code>reduce</code>.</p>

<p>What would be an equally concise rewrite of this for Python3?</p>
