How to use the tartube.downloads.DownloadManager function in tartube

def __init__(self, app_obj, operation_type, download_list_obj):

        if DEBUG_FUNC_FLAG:
            utils.debug_time('dld 113 __init__')

        super(DownloadManager, self).__init__()

        # IV list - class objects
        # -----------------------
        # The mainapp.TartubeApp object
        self.app_obj = app_obj
        # Each instance of this object, which represents a single download
        #   operation, creates its own options.OptionsParser object. That
        #   object convert the download options stored in
        #   downloads.DownloadWorker.options_list into a list of youtube-dl
        #   command line options
        self.options_parser_obj = None
        # An ordered list of media data objects to download, each one
        #   represented by a downloads.DownloadItem object
        self.download_list_obj = download_list_obj
        # List of downloads.DownloadWorker objects, each one handling one of
        #   several simultaneous downloads