code: protected void validateDeclaredReturns() {
          boolean returnsObject = void.class != method.getReturnType();
          if (returnsObject) {
              for (Return declaredReturn : declaredReturns) {
                  if (declaredReturn.code() >= 200 && declaredReturn.code() < 300) {
                      return;
                  }
              }
              throw new FatalException("{} returns an object but does not declare a successful @{}(code=200, onResult={}.class)",
                      Util.toString(method), Return.class.getSimpleName(), method.getReturnType().getSimpleName());
          }
      }
docs: Validates the declared Returns of the controller method.  If the controller method returns an object then
  it must also declare a successful @Return with a status code in the 200 range.