问在Swift中使用AVPlayer的webVTT包括头部的一些例子？

EN

    let token: String = "xyz"

    let videoUrl = URL(string: "...url/video.mp4")!
    let vttURL = URL(string: "...url/subtitle.vtt")!

    let videoPlusSubtitles = AVMutableComposition()

    let headers: [AnyHashable : Any] = [
        "content-type": "application/json",
        "authorization": "Bearer \(token)"
    ]
    let videoAsset = AVURLAsset(url: videoUrl)
    let subtitleAsset = AVURLAsset(url: vttURL, options: ["AVURLAssetHTTPHeaderFieldsKey": headers])