Type.Container
type family Index2 idx cont :: el
type family Append el cont :: k
type family Insert el cont :: k
type family Remove el cont :: k
type family Reverse cont :: k
type family Unique cont :: k
type family Concat a b :: k
type family Diff c c' :: k
type family Union c c' :: k
type family a <> b
type family FromJust a
type UnsafeIndex el cont