title: python set of tuple intersection
body: <p>If I have two sets of tuples, is there a way to get the intersection only matching on the first element of the tuple?</p>
  
  <p>I would be able to specify this at set/frozenset creation time if need be.</p>
  
  <p>If it helps, I am trying to do a JOIN on two sets of tuple based on the first values in the tuples</p>