code: def insert(self, objects, index=0):
          
          objects = (objects,)
          for child in objects:
              if not isinstance(child, Element):
                  raise Exception("append %s not-valid" %
                      (child.__class__.__name__,))
              self.children.insert(index, child)
              child.parent = self
          return self
docs: Insert an L{Element} content at the specified index.
  
          @param objects: A (single|collection) of attribute(s) or element(s) to
              be added as children.
          @type objects: (L{Element}|L{Attribute})
          @param index: The position in the list of children to insert.
          @type index: int
          @return: self
          @rtype: L{Element}