Nevow basic container Page + Page/Element with Data

Here some small code - snippets where some form of data gets passed to a page / element. This could of course be changed to get more data or not a dict/axiom db but I prefer it this way (Pretty much every axiom/nevow app will need something like this afaik):

# -*- coding: utf8 -*-

from nevow.rend import Page
from nevow.page import Element, renderer
from nevow import loaders
from nevow import tags as T

class PageWithDB(Page):
    """
    Own Page class to save myself passing the db object to every sub-page
    """
    
    def __init__(self, db, original = None, docFactory = None):
        self.db = None
        if not db:
            raise ValueError("No Database given")
        self.db = db
        Page.__init__(self, original, docFactory)

class ElementWithData(Element):
    """
    Element with Data
    """
        
    def __init__(self, data, docFactory = None):
        self.data = None
        if data == None:
            raise ValueError("No Data")
        self.data = data
        Element.__init__(self, docFactory)

class ContainerPage(PageWithDB):
    """
    Container Page which just has title and content renderer and
    loads only skeleton page. To be used with Elements
    
    The render_title and render_content methods should be overridden
    """
    addSlash = True
    docFactory = loaders.xmlfile(u'templates/pageskel.xml')
    
    def render_title(self, ctx, data):
        return u'TITLE RENDER'
    
    def render_content(self, ctx, data):
        return u'CONTENT'

The ContainerPage class is just a small class where I render the title as actual and on top of the page. The template is of course flexible. I use this to override render_content and then return a list of Elements, stan, ..
Here is the template I use (it is very basic as what I write at the moement is a very simple webapp):

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
      Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="de" xml:lang="de"
    xmlns:nevow="http://nevow.com/ns/nevow/0.1">
<head>
    <title><span nevow:render="title" /></title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
    <h1><span nevow:render="title" /></h1>
    <span nevow:render="content" />
</body>
</html>