code: @Override
      public void writeStartElement(String localName)
          throws XMLStreamException
      {
          checkStartElement(localName, null);
          if (mValidator != null) {
              mValidator.validateElementStart(localName, XmlConsts.ELEM_NO_NS_URI, XmlConsts.ELEM_NO_PREFIX);
          }
          mEmptyElement = false;
          if (mOutputElemPool != null) {
              SimpleOutputElement newCurr = mOutputElemPool;
              mOutputElemPool = newCurr.reuseAsChild(mCurrElem, localName);
              --mPoolSize;
              mCurrElem = newCurr;
          } else {
              mCurrElem = mCurrElem.createChild(localName);
          }
  
          doWriteStartTag(localName);
      }
docs: This method is assumed to just use default namespace (if any),
  and no further checks should be done.