Question about ApplyTransformers

I have doubts about this code:

xmldsigjs/src/signed_xml.ts

Lines 544 to 573 in 71e66d3

	protected ApplyTransforms(transforms: XmlTransforms, input: Element): any {
	let output: any = null;
	transforms.Sort((a, b) => {
	const c14nTransforms = [Transforms.XmlDsigC14NTransform, XmlDsigC14NWithCommentsTransform,
	Transforms.XmlDsigExcC14NTransform, XmlDsigExcC14NWithCommentsTransform];
	if (c14nTransforms.some((t) => a instanceof t)) {
	return 1;
	}
	if (c14nTransforms.some((t) => b instanceof t)) {
	return -1;
	}
	return 0;
	}).ForEach((transform) => {
	transform.LoadInnerXml(input);
	if (transform instanceof Transforms.XmlDsigXPathTransform) {
	transform.GetOutput();
	} else {
	output = transform.GetOutput();
	}
	});
	// Apply C14N transform if Reference has only one transform EnvelopedSignature
	if (transforms.Count === 1 && transforms.Item(0) instanceof Transforms.XmlDsigEnvelopedSignatureTransform) {
	const c14n = new Transforms.XmlDsigC14NTransform();
	c14n.LoadInnerXml(input);
	output = c14n.GetOutput();
	}
	return output;
	}

1. Why there is "dummy" GetOutput call at 560?
2. Why every transformer load initial xml (line 585) instead of the result returned by the predecessor? It look like only last transformer works.