code: protected ConstantField processField(Class<?> aClass, Field field) {
          Constant annot = field.getAnnotation(Constant.class);
          if (annot != null) {
              return factory.createConstantField(aClass, field.getName(), annot);
          }
  
          return null;
      }
docs: Converts a field/potential-constant into a ConstantField.
  Returns null if the field cannot be constant.
  Override this to change how fields are processed.
  @param aClass the class the field came from
  @param field the field
  @return a ConstantField or null