code: def vocab_marking_definition(instance):
      
      if (instance['type'] == 'marking-definition' and
              'definition_type' in instance and not
              instance['definition_type'] in enums.MARKING_DEFINITION_TYPES):
  
          return JSONError("Marking definition `definition_type` should be one "
                           "of: %s." % ', '.join(enums.MARKING_DEFINITION_TYPES),
                           instance['id'], 'marking-definition-type')
docs: Ensure that the `definition_type` property of `marking-definition`
      objects is one of the values in the STIX 2.0 specification.