How to use the flasgger.utils.parse_definition_docstring function in flasgger

# set defaults from template
        if self.template is not None:
            data.update(self.template)

        paths = data['paths']
        definitions = data['definitions']
        ignore_verbs = set(
            self.config.get('ignore_verbs', ("HEAD", "OPTIONS"))
        )

        # technically only responses is non-optional
        optional_fields = self.config.get('optional_fields') or OPTIONAL_FIELDS

        for name, def_model in self.get_def_models(
                spec.get('definition_filter')).items():
            description, swag = parse_definition_docstring(
                def_model, self.sanitizer)
            if name and swag:
                if description:
                    swag.update({'description': description})
                definitions[name].update(swag)

        specs = get_specs(
            self.get_url_mappings(spec.get('rule_filter')), ignore_verbs,
            optional_fields, self.sanitizer,
            doc_dir=self.config.get('doc_dir'))

        http_methods = ['get', 'post', 'put', 'delete']
        for rule, verbs in specs:
            operations = dict()
            for verb, swag in verbs:
                update_dict = swag.get('definitions', {})