code: def defaultNamespace(self):
          
          p = self
          while p is not None:
              if p.expns is not None:
                  return None, p.expns
              p = p.parent
          return Namespace.default
docs: Get the default (unqualified namespace).
  
          This is the expns of the first node (looking up the tree) that has it
          set.
  
          @return: The namespace of a node when not qualified.
          @rtype: (I{prefix}, I{name})