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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 do(self, command):
 """ "Executes" the given command on the virtual device, and returns the response. :type command: str :param command: The command to be executed. :rtype: str :return: The response of the virtual device. """

        echo = self.echo and command or ''
        if not self.logged_in:
            return echo + '\n' + self._get_prompt()

        response = self.commands.eval(command)
        if response is None:
            return echo + '\n' + self._get_prompt()
        return echo + response