anchor.diff:      |> Seq.map (fun (k, v) -> v)
       |> Seq.head
       |> fun x -> x.Split [|';'|]
  -    |> List.ofSeq
  -    |> List.fold(fun acc elem -> match acc with
  +    |> Seq.fold(fun acc elem -> match acc with
                                    | Some(r) -> Some(r)
                                    | _       -> match elem with
                                                 | "text/json" -> Some(Json)
  
positive.code:                   let! state = commanderRoute commander
                    let! f = FormatExtractor request format
                    let! timestamp = timeRoute timestampString
                    return state.Operations
                            |> List.ofSeq
                            |> List.filter
                              (fun e -> match e.Timestamp with
                                        | t when t >= timestamp -> true
                                        | _                     -> false)
  
negative.code: 
    let MimeType = 
      function
      | Xml   -> Writers.setMimeType "text/xml; charset=utf-8"
      | Json  -> Writers.setMimeType "text/json; charset=utf-8"
      | Csv   -> Writers.setMimeType "text/csv; charset=utf-8"
  
    let app =
      choose
  