docs: private void parseCT_RElt(XMLEventReader xmlEventReader, StringBuilder buf) throws XMLStreamException {
      // Precondition: pointing to <r>;  Post condition: pointing to </r>
      XMLEvent xmlEvent;
      while((xmlEvent = xmlEventReader.nextTag()).isStartElement()) {
        switch(xmlEvent.asStartElement().getName().getLocalPart()) {
          case "t": // Text
            buf.append(xmlEventReader.getElementText());
            break;
          case "rPr": // Run Properties
            skipElement(xmlEventReader);
            break;
          default:
            throw new IllegalArgumentException(xmlEvent.asStartElement().getName().getLocalPart());
        }
      }
    }