docs: def check_attribute_exists(instance):
      """ Additional check for the dimension model, to ensure that attributes
      given as the key and label attribute on the dimension exist. """
      attributes = instance.get('attributes', {}).keys()
      if instance.get('key_attribute') not in attributes:
          return False
      label_attr = instance.get('label_attribute')
      if label_attr and label_attr not in attributes:
          return False
      return True