old_contents: 
  from nose.tools import *
  
  from dit.algorithms.lattice import sigma_algebra_sort
  
  def test_sigalg_sort():
  	sigalg = frozenset([
  		frozenset([]),
  		frozenset([1]),
  		frozenset([2]),
  		frozenset([1,2])
  	])
  	sigalg_ = [(), (1,), (2,), (1,2)]
  	assert_equal( sigalg_, sigma_algebra_sort(sigalg) )
  
new_contents: from __future__ import division
  
  from iterutils import powerset
  
  from nose.tools import *
  
  from dit import Distribution
  from dit.algorithms.lattice import *
  
  def test_sigalg_sort():
  	sigalg = frozenset([
  		frozenset([]),
  		frozenset([1]),
  		frozenset([2]),
  		frozenset([1,2])
  	])
  	sigalg_ = [(), (1,), (2,), (1,2)]
  	assert_equal( sigalg_, sigma_algebra_sort(sigalg) )
  
  def test_join_sigalg():
      outcomes = ['00', '01', '10', '11']
      pmf = [1/4]*4
      d = Distribution(outcomes, pmf)
      sigalg = frozenset([ frozenset(_) for _ in powerset(outcomes) ])
      join = join_sigalg(d, [[0],[1]])
      assert_equal(sigalg, join)
  
  def test_meet_sigalg():
      outcomes = ['00', '01', '10', '11']
      pmf = [1/4]*4
      d = Distribution(outcomes, pmf)
      sigalg = frozenset([ frozenset([]), frozenset(outcomes) ])
      meet = meet_sigalg(d, [[0],[1]])
      assert_equal(sigalg, meet)
subject: add a couple lattice tests