Parse the line provided previously by gstvideo.video_vbiparser.VideoVBIParser.addLine.
a #GstVideoAncillary to start the eventual ancillary data
gstvideo.types.VideoVBIParserResult.Ok if ancillary data was found and anc was filled. gstvideo.types.VideoVBIParserResult.Done if there wasn't any data.
Parse the line provided previously by gstvideo.video_vbiparser.VideoVBIParser.addLine.