code: def refitPrefixes(self):
          
          for c in self.children:
              c.refitPrefixes()
          if self.prefix is not None:
              ns = self.resolvePrefix(self.prefix)
              if ns[1] is not None:
                  self.expns = ns[1]
          self.prefix = None
          self.nsprefixes = {}
          return self
docs: Refit namespace qualification by replacing prefixes
          with explicit namespaces. Also purges prefix mapping table.
          @return: self
          @rtype: L{Element}