anchor.diff:  % Utility functions
   %
   
  -format_to_content_type('pb') -> "application/protobuf";
  +format_to_content_type('pb') -> "application/x-protobuf";
   format_to_content_type('json') -> "application/json";
   format_to_content_type('piq') -> "text/plain".
   
   
  -content_type_to_format("application/protobuf") -> 'pb';
  +content_type_to_format("application/x-protobuf") -> 'pb';
   content_type_to_format("application/json") -> 'json';
   content_type_to_format("text/plain") -> 'piq';
   content_type_to_format(_) -> 'undefined'.
  
positive.code: %-define(DEBUG, 1).
  -include("debug.hrl").
  
  
  % XXX: or use "application/octet-stream" Content-Type instead of
  % "application/protobuf"?
  
  % XXX: set charset=UTF-8 in "Content-Type" response header for text (Piq), Json
  % and XML responses?
  
negative.code:     IsKnownType =
          case wrq:get_req_header("content-type", ReqData) of
              "application/json" -> true;
              "application/x-protobuf" -> true;
              % allow content-type to be undefined when the body is empty
              'undefined' when IsEmptyBody -> true;
              _ -> false
  