293     def rev(self, node):

   293     def rev(self, node):

   294         try:

   294         try:

   295             return self._nodecache[node]

   295             return self._nodecache[node]

   296         except KeyError:

   296         except KeyError:

   297             n = self._nodecache

   297             n = self._nodecache

   300             i = self.index

   298             i = self.index

   301             p = self._nodepos

   299             p = self._nodepos

   302             if p is None:

   300             if p is None:

   303                 p = len(i) - 2

   301                 p = len(i) - 2

   304             for r in xrange(p, -1, -1):

   302             for r in xrange(p, -1, -1):