title: Python: powerset of a given set with generators
body: <p>I am trying to build a list of subsets of a given set in Python with <strong>generators</strong>. Say I have </p>
  
  <p><code>set([1, 2, 3])</code> </p>
  
  <p>as input, I should have </p>
  
  <p><code>[set([1, 2, 3]), set([2, 3]), set([1, 3]), set([3]), set([1, 2]), set([2]), set([1]), set([])]</code> </p>
  
  <p>as output. How can I achieve this?</p>