docs: public Type makeSomethingFromGTS(List<Element> children) throws Exception {
  		if (children.isEmpty())
  			return null;
  		if (children.size() == 1) {
  			String type = children.get(0).getAttribute("xsi:type");
  			if (type.equals("IVL_TS"))
  				return makePeriodFromIVL(children.get(0));
  			else
  				throw new Exception("Unknown GTS type '"+type+"'");
  		}
  		CommaSeparatedStringBuilder t = new CommaSeparatedStringBuilder();
  		for (Element c : children)
  			t.append(c.getAttribute("xsi:type"));
  		if (t.toString().equals("IVL_TS, PIVL_TS"))
  			return makeTimingFromBoundedPIVL(children.get(0), children.get(1));
  		if (t.toString().equals("IVL_TS, EIVL_TS"))
  			return makeTimingFromBoundedEIVL(children.get(0), children.get(1));
    	throw new Exception("Unknown GTS pattern '"+t.toString()+"'");
    }