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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def __driver_completer(self, toks, text, state):
 """Driver level completer. Arguments: toks: A list of tokens, tokenized from the original input line. text: A string, the text to be replaced if a completion candidate is chosen. state: An integer, the index of the candidate out of the list of candidates. Returns: A string, the candidate. """

        if state != 0:
            return self.__completion_candidates[state]

        # Update the cache when this method is first called, i.e., state == 0.

        # If the line is empty or the user is still inputing the first token,
        # complete with available commands.
        if not toks or (len(toks) == 1 and text == toks[0]):
            try:
                self.__completion_candidates = self.__complete_cmds(text)
            except:
                self.stderr.write('\n')
                self.stderr.write(traceback.format_exc())
                self.__completion_candidates = []
            return self.__completion_candidates[state]

        # Otherwise, try to complete with the registered completer method.
        cmd = toks[0]
        args = toks[1:] if len(toks) > 1 else None
        if text and args:
            del args[-1]
        if cmd in self._completer_map.keys():
            completer_name = self._completer_map[cmd]
            completer_method = getattr(self, completer_name)
            try:
                self.__completion_candidates = completer_method(cmd, args, text)
            except:
                self.stderr.write('\n')
                self.stderr.write(traceback.format_exc())
                self.__completion_candidates = []
        else:
            self.__completion_candidates = []

        return self.__completion_candidates[state]