code: def append(self, node):
          
          if isinstance(node, basestring):
              self.__root = Element(node)
              return
          if isinstance(node, Element):
              self.__root = node
              return
docs: Append (set) the document root.
          @param node: A root L{Element} or name used to build
              the document root element.
          @type node: (L{Element}|str|None)