Return an ordered list of unordered pairs in l.
abjad> listtools.get_unordered_pairs([1, 2, 3, 4])
[set([1, 2]), set([1, 3]), set([1, 4]), set([2, 3]), set([2, 4]), set([3, 4])]
abjad> listtools.get_unordered_pairs([1, 2])
[set([1, 2])]
abjad> listtools.get_unordered_pairs([1])
[]
abjad> listtools.get_unordered_pairs([ ])
[]
Note
This function returns a list instead of a generator.