848         error.LookupError is raised if an ambiguous node specified.

   848         error.LookupError is raised if an ambiguous node specified.

   849         """

   849         """

   850         try:

   850         try:

   851             self[changeid]

   851             self[changeid]

   852             return True

   852             return True

   855             return False

   854             return False

   856 

   855 

   857     def __nonzero__(self):

   856     def __nonzero__(self):

   858         return True

   857         return True

   859 

   858