code: def open_vocab_values(instance):
      
      if instance['type'] not in enums.VOCAB_PROPERTIES:
          return
  
      properties = enums.VOCAB_PROPERTIES[instance['type']]
      for prop in properties:
          if prop in instance:
  
              if type(instance[prop]) is list:
                  values = instance[prop]
              else:
                  values = [instance[prop]]
  
              for v in values:
                  if not v.islower() or '_' in v or ' ' in v:
                      yield JSONError("Open vocabulary value '%s' should be all"
                                      " lowercase and use hyphens instead of"
                                      " spaces or underscores as word"
                                      " separators." % v, instance['id'],
                                      'open-vocab-format')
docs: Ensure that the values of all properties which use open vocabularies are
      in lowercase and use hyphens instead of spaces or underscores as word
      separators.