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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 init(self):
 """ Init or reset the virtual device. :rtype: str :return: The initial response of the virtual device. """

        self.logged_in = False

        if self.login_type == self.LOGIN_TYPE_PASSWORDONLY:
            self.prompt_stage = self.PROMPT_STAGE_PASSWORD
        elif self.login_type == self.LOGIN_TYPE_NONE:
            self.prompt_stage = self.PROMPT_STAGE_CUSTOM
        else:
            self.prompt_stage = self.PROMPT_STAGE_USERNAME

        return self.banner + self._get_prompt()