code: function (methodName) {
              var params = this.getParameters(methodName),
                  ret;
              params.forEach(function (param) {
                  if (param && (param.envelope === 'JSON' ||
                          param.envelope === 'ENTITY')) {
                      ret = param;
                  }
              });
              return ret;
          }
docs: Returns the parameter associated with the payload of a request if there is one.
  @param methodName - the service method to return a payload schema for.
  @return the payload parameter or undefined