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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 list_users(self):
 """ Run the ``list_users`` command and return a list of tuples describing the users. :return: A list of 2-element tuples. The first element is the username, the second a list of tags for the user. """

        lines = output_lines(self.exec_rabbitmqctl_list('users'))
        return [_parse_rabbitmq_user(line) for line in lines]