code: def start(self, tag, attrs):
          
          if self._level == 0:
              self._root = ElementTree.Element(tag, attrs)
              self._handler.stream_start(self._root)
          if self._level < 2:
              self._builder = ElementTree.TreeBuilder()
          self._level += 1
          return self._builder.start(tag, attrs)
docs: Handle the start tag.
  
          Call the handler's 'stream_start' methods with
          an empty root element if it is top level.
  
          For lower level tags use :etree:`ElementTree.TreeBuilder` to collect
          them.