type Unpickle<'a> = ILiteReadStream -> 'a
// fmap
let inline (|>>) (u: Unpickle<'a>) (f: 'a -> 'b) : Unpickle<'b> =
    fun stream -> f (u stream)


type Pickle<'a> = 'a -> ILiteWriteStream -> unit
// reverse or backwards fmap?
let inline (<<|) (p: Pickle<'b>) (f: 'a -> 'b) : Pickle<'a> =
    fun a' stream -> p (f a') stream