Example from README does not compile about fleece HOT 3 CLOSED

type PersonF = { 
    name : string * string
    age : int option
    children: PersonF list }
    with
    static member JsonObjCodec =
        fun f l a c -> { name = (f, l); age = a; children = c }
        |> withFields
        |> jfield    "firstName" (fun x -> fst x.name)
        |> jfield    "lastName"  (fun x -> snd x.name)
        |> jfieldOpt "age"       (fun x -> x.age)
        |> jfieldWith jsonValueCodec "children"  (fun x -> x.children)

#r "nuget: Fleece.SystemJson, 0.10.0"
#r "nuget: System.Json, 4.7.1"
open System.Json
open Fleece.SystemJson
open Fleece.SystemJson.Operators

type PersonF = { 
    name : string * string
    age : int option
    children: PersonF list }
    with
    static member JsonObjCodec =
        fun f l a c -> { name = (f, l); age = a; children = c }
        |> withFields
        |> jfield    "firstName" (fun x -> fst x.name)
        |> jfield    "lastName"  (fun x -> snd x.name)
        |> jfieldOpt "age"       (fun x -> x.age)
        |> jfield    "children"  (fun x -> x.children)