New in version 2.0.
Get sequence elements frequency distribution:
abjad> from abjad.tools import sequencetools
abjad> sequencetools.get_sequence_elements_frequency_distribution([1, 3, 3, 3, 2, 1, 1, 2, 3, 3, 1, 2])
[(1, 4), (2, 3), (3, 5)]
Return list of element / count pairs.