无法构建angularjs doc(不知道如何格式化@ngdoc:方法)

我有一些带有一些文档的服务,但是当我尝试使用grunt-ngdocs构建文档时,它失败了:

Warning: Don't know how to format @ngdoc: method Use --force to continue.

这是我想要做的

(function(angular) {
    'use strict';

    angular.module('services.base64', [])
    .factory(
            'Base64',
            [function() {

                /**
                 * @ngdoc service
                 * @name Base64
                 * @module services.base64
                 * @description Provides encoding a string into base64, and decode base64 to a string
                 */
                return {
                    /**
                     * @ngdoc method
                     * @name Base64#encode
                     * @param {string}
                     *            input the string you want to encode as base64
                     * @returns {string} the base64 encoded string
                     */
                    encode : function(input) {
                        //...
                    },

                    /**
                     * @ngdoc method
                     * @name Base64#decode
                     * @param {string}
                     *            input the base64 encoded string
                     * @returns {string} the decoded string
                     */
                    decode : function(input) {
                        //...
                    }
                };
            }]);
}(angular));

我确定我错过了一些简单的东西......