How to use the jsonargparse.ActionJsonSchema._extend_jsonvalidator_with_default function in jsonargparse

if 'ext_vars' in kwargs or 'schema' in kwargs:
            import_jsonnet('ActionJsonnet')
            _check_unknown_kwargs(kwargs, {'schema', 'ext_vars'})
            if 'ext_vars' in kwargs and not isinstance(kwargs['ext_vars'], (str, type(None))):
                raise ValueError('ext_vars has to be either None or a string.')
            self._ext_vars = kwargs['ext_vars'] if 'ext_vars' in kwargs else None
            schema = kwargs['schema'] if 'schema' in kwargs else None
            if schema is not None:
                import_jsonschema('ActionJsonnet')
                if isinstance(schema, str):
                    try:
                        schema = yaml.safe_load(schema)
                    except Exception as ex:
                        raise type(ex)('Problems parsing schema :: '+str(ex))
                jsonvalidator.check_schema(schema)
                self._validator = ActionJsonSchema._extend_jsonvalidator_with_default(jsonvalidator)(schema)
            else:
                self._validator = None
        elif '_ext_vars' not in kwargs or '_validator' not in kwargs:
            raise ValueError('Expected ext_vars and/or schema keyword arguments.')
        else:
            self._ext_vars = kwargs.pop('_ext_vars')
            self._validator = kwargs.pop('_validator')
            kwargs['type'] = str
            super().__init__(**kwargs)