anchor.diff:  
           { Parse = userInfoP
             Format = userInfoF }
  +
  +    (* Lenses *)
  +
  +    static member UserInfo_ =
  +        (fun (UserInfo u) -> u), (fun u -> UserInfo u)
   
   (* Section 3.2.2 *)
   
  
positive.code:         { Parse = relativeReferenceP
            Format = relativeReferenceF }
  
      static member Format =
          Formatting.format RelativeReference.Mapping.Format
  
  
negative.code: 
          let queryP =
              parser |>> Query
  
          let queryF =
              function | Query x -> formatter x
  
          { Parse = queryP
            Format = queryF }
  
      (* Lenses *)
  
      static member Query_ =
          (fun (Query q) -> q), (fun q -> Query q)
  
      (* Common *)
  
      static member Format =
          Formatting.format Query.Mapping.Format
  