anchor.diff:  
   http_request(R = #request{}) ->
     Body = case R#request.body of
  -    undefined -> <<>>;
  -    Bin       -> Bin
  +    null -> <<>>;
  +    Bin  -> Bin
     end,
     lhttpc:request( R#request.url
                   , R#request.method
  
positive.code:   Rsp#response{ body = maybe_parse_body(Hdrs, RawBody)
                }.
  
  maybe_parse_body(_Hdrs, undefined) ->
    undefined;
  maybe_parse_body(Hdrs, Body) ->
    case is_json_body(Hdrs, Body) of
      true  -> parse_json(Body);
  
negative.code:   Url = make_request_url(Params, substitute(extract(Url0), SubVars)),
    Req#request{ url  = Url
               , headers = Hdrs
               , body = from_utf8(RawBody)
               }.
  
  make_response(#response{headers=Hdrs, body=RawBody0} = Rsp, SubVars) ->
  