code: def append(self, objects):
          
          if not isinstance(objects, (list, tuple)):
              objects = (objects,)
          for child in objects:
              if isinstance(child, Element):
                  self.children.append(child)
                  child.parent = self
                  continue
              if isinstance(child, Attribute):
                  self.attributes.append(child)
                  child.parent = self
                  continue
              raise Exception("append %s not-valid" %
                  (child.__class__.__name__,))
          return self
docs: Append the specified child based on whether it is an element or an
          attribute.
  
          @param objects: A (single|collection) of attribute(s) or element(s) to
              be added as children.
          @type objects: (L{Element}|L{Attribute})
          @return: self
          @rtype: L{Element}