code: def append(self, name, attrs=None, data=None):
          
          elem = self.__class__(name, attrs, data, parent=self, index=len(self._children))
          self._children.append(elem)
          return elem
docs: Called when the parser detects a start tag (child element) while in this node. Internally creates an
          :class:`XmlElement` and adds it to the end of this node's children.
  
          :param name: The tag name to add
          :param attrs: Attributes for the new tag
          :param data: CDATA for the new tag
          :returns: The newly-created element
          :rtype: :class:`XmlElement`