code: def resolvePrefix(self, prefix):
          
          ns = Namespace.default
          if self.parent is not None:
              ns = self.parent.resolvePrefix(prefix)
          return ns
docs: Resolve the specified prefix to a known namespace.
          @param prefix: A declared prefix
          @type prefix: basestring
          @return: The namespace that has been mapped to I{prefix}
          @rtype: (I{prefix}, I{name})