code: private boolean isRequired(Field field) {
          return field.getAnnotation(Require.class) != null
                  // Use the field's declaring class for RequireAll; may be a super class
                  || (field.getDeclaringClass().getAnnotation(RequireAll.class) != null
                  && field.getAnnotation(NotRequired.class) == null);
      }
docs: Determines whether a field is required or not based on combination of Require, RequireAll,
  and NotRequired annotations.