<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iterate(self, path):
 """ Returns a recursive iterator on the specified key and its subkeys. @type path: str @param path: Registry key path. @rtype: iterator @return: Recursive iterator that returns Registry key paths. @raise KeyError: The specified path does not exist. """

        if path.endswith('\\'):
            path = path[:-1]
        if not self.has_key(path):
            raise KeyError(path)
        stack = collections.deque()
        stack.appendleft(path)
        return self.__iterate(stack)