我正在尝试将代码从Swift 2版本迁移到Swift 3版本。我无法迁移以下代码部分，也没有找到任何解决方案。我该怎么做？

//标记：URLRequestConvertible

     public var URLRequest: NSMutableURLRequest {
            let urlComponent = NSURLComponents(string: Router.baseURL)!
            urlComponent.path = Router.basePath.stringByAppendingString(path)

            let mutableURLRequest = NSMutableURLRequest(URL: urlComponent.URL!)
            mutableURLRequest.HTTPMethod = method.rawValue

            var parameters: [String: AnyObject] = Dictionary()
            parameters["key"] = Router.key
            parameters["hl"] = "en"

            switch self {
            case .getMostPopularVideos(let pageToken):
                parameters["part"] = "snippet,contentDetails,statistics"
                parameters["chart"] = "mostPopular"
                parameters["videoCategoryId"] = TubeTrends.Settings.topTrendsCat
                if let pageToken = pageToken {
                        parameters["pageToken"] = pageToken
                }
                return Alamofire.ParameterEncoding.URL.encode(mutableURLRequest, parameters: parameters).0  //This part Giving Error like Alamofire Type 'ParameterEncoding' has no member 'URL'

//            default:
//                return mutableURLRequest
            }
        }
    }