How to use the imsc.fromXML function in imsc

if (currentImageId) {
                    accumulated_image_data = accumulated_image_data + contents;
                }
            }
        };

        if (!data) {
            errorMsg = 'no ttml data to parse';
            throw new Error(errorMsg);
        }

        content.data = data;

        eventBus.trigger(Events.TTML_TO_PARSE, content);

        const imsc1doc = fromXML(content.data, function (msg) {
            errorMsg = msg;
        }, metadataHandler);

        eventBus.trigger(Events.TTML_PARSED, {ttmlString: content.data, ttmlDoc: imsc1doc});

        const mediaTimeEvents = imsc1doc.getMediaTimeEvents();

        for (i = 0; i < mediaTimeEvents.length; i++) {
            let isd = generateISD(imsc1doc, mediaTimeEvents[i], function (error) {
                errorMsg = error;
            });

            if (isd.contents.some(topLevelContents => topLevelContents.contents.length)) {
                //be sure that mediaTimeEvents values are in the mp4 segment time ranges.
                startTime = (mediaTimeEvents[i] + offsetTime) < startTimeSegment ? startTimeSegment : (mediaTimeEvents[i] + offsetTime);
                endTime = (mediaTimeEvents[i + 1] + offsetTime) > endTimeSegment ? endTimeSegment : (mediaTimeEvents[i + 1] + offsetTime);