docs: public DateTimeType makeDateTimeFromIVL(Element ivl) throws Exception {
  	  if (ivl == null)
  	  	return null;
  	  if (ivl.hasAttribute("value")) 
  	  	return makeDateTimeFromTS(ivl);
  	  Element high =  cda.getChild(ivl, "high");
  	  if (high != null)
  	  	return makeDateTimeFromTS(high);
  	  Element low =  cda.getChild(ivl, "low");
  	  if (low != null)
  	  	return makeDateTimeFromTS(low);
  	  return null;
    }