anchor.diff:      /// </summary>
       /// <param name="config">The configuration to apply to the request.</param>
       /// <param name="request">The request to permute.</param>
  -    let applyConfiguration config (request:INapRequest) =
  +    let applyConfiguration config (request:INapRequest) : INapRequest =
           (request :?> NapRequest).ApplyConfig config
  +        |> fun req -> upcast req
       
       /// <summary>
       /// Update the configuration to use the serializer specified.
  
positive.code:     /// </summary>
      /// <param name="f">The configuration function that accepts the current configuration and outputs the new configuration.</param>
      /// <param name="request">The request to permute.</param>
      let configure f (request:INapRequest) =
          f (request.Advanced().Configuration) |> (request :?> NapRequest).ApplyConfig
      
      /// <summary>
      /// Retrieve the configuration stored for a given request.
  
negative.code:         configure (fun c -> c.AddSerializer serializer)
      
      let useSerializerFor contentType serializer =
          (configure <| fun c -> c.AddSerializerFor contentType serializer)
  
      let logUsing logger (request:INapRequest) : INapRequest =
          (request :?> NapRequest).ApplyConfig (
              (request :?> NapRequest).Config.SetLogging logger
          )
          |> fun req -> upcast req
  
  module Resp =
      let chain method url (response:NapResponse) =
  