docs: public void writeAttribute(final String uri, final String qName, final String value) {
          if (!openStartElement) {
              throw new IllegalStateException("Current state does not allow Attribute writing");
          }
          if (openAttributes == null) {
              openAttributes = new AttributesImpl();
          }
          final QName att = new QName(uri, qName);
          addNamespace(uri, att.prefix, elementStack.getFirst()); // peek
          openAttributes.addAttribute(uri, att.localName, qName, "CDATA", value);
      }