map length (tiers :: [[ Map () () ]])  =  [1,1]

length (list :: [ Map () () ])  =  2

allUnique (list :: [ Map () () ])  =  True

ratioRepetitions (list :: [ Map () () ])  =  0 % 1

tiers :: [Map () ()]  =
  [ [Map []]
  , [Map [((),())]]
  ]