anchor.diff:  content_type_to_format(_) -> 'undefined'.
   
   
  -get_req_body(ReqData) ->
  -    % for some reason, Webmachine returns <<>> as a body even if
  -    % "Content-Length" header is not present.
  -    case wrq:req_body(ReqData) of
  -        'undefined' -> 'undefined';
  -        <<>> -> 'undefined';
  -        X -> X
  -    end.
  -
  -
   set_data_response(Data, OutputFormat, ReqData) ->
       wrq:set_resp_header(
           "Content-Type", format_to_content_type(OutputFormat),
  
positive.code: 
  -record(context, {
      rpc_mod,  % Piqi-RPC skeleton module generated by piqic-erlang-rpc
      impl_mod  % Piqi-RPC implementation module containing callback functions
  }).
  
  
  
negative.code:     RpcMod = Context#context.rpc_mod,
      ImplMod = Context#context.impl_mod,
  
      % this field is initialized above by the known_content_type/2 function
      InputData = Context#context.request_body,
  
      % make the actual call
      RpcResponse = RpcMod:rpc(ImplMod, FuncName, InputData, InputFormat, OutputFormat),
  
  