code: function isJsonRepresentation(contentType, returnType, options) {
    return (mediaTypeContainsJson(contentType) || mediaTypeContainsJson(returnType)) ? options.fn(this) : options.inverse(this);
  }
docs: decides if this request/response has a JSON representation
  @param {string} contentType    the media type of the request
  @param {string} returnType     the media type of the response