docs: def getDocFactory(self, name, default=None):
          """
          Locate a L{nevow.inevow.IDocFactory} object with the given name from
          the themes installed on the site store and return it.
          """
          loader = None
          for theme in getInstalledThemes(self.siteStore):
              loader = theme.getDocFactory(name)
              if loader is not None:
                  return loader
          return default