code: def custom_object_prefix_strict(instance):
      
      if (instance['type'] not in enums.TYPES and
              instance['type'] not in enums.RESERVED_OBJECTS and
              not CUSTOM_TYPE_PREFIX_RE.match(instance['type'])):
          yield JSONError("Custom object type '%s' should start with 'x-' "
                          "followed by a source unique identifier (like a "
                          "domain name with dots replaced by hyphens), a hyphen "
                          "and then the name." % instance['type'],
                          instance['id'], 'custom-prefix')
docs: Ensure custom objects follow strict naming style conventions.