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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 restart(self, restart_data, run_async=False):
 """ conditional and unconditional restart """

        assert isinstance(restart_data, dict)

        if (not self.restart_matches(restart_data.get('role'),
                                     restart_data.get('postgres_version'),
                                     ('restart_pending' in restart_data))):
            return (False, "restart conditions are not satisfied")

        with self._async_executor:
            prev = self._async_executor.schedule('restart')
            if prev is not None:
                return (False, prev + ' already in progress')

            # Make the main loop to think that we were recovering dead postgres. If we fail
            # to start postgres after a specified timeout (see below), we need to remove
            # leader key (if it belong to us) rather than trying to start postgres once again.
            self.recovering = True

        # Now that restart is scheduled we can set timeout for startup, it will get reset
        # once async executor runs and main loop notices PostgreSQL as up.
        timeout = restart_data.get('timeout', self.patroni.config['master_start_timeout'])
        self.set_start_timeout(timeout)

        # For non async cases we want to wait for restart to complete or timeout before returning.
        do_restart = functools.partial(self.state_handler.restart, timeout, self._async_executor.critical_task)
        if self.is_synchronous_mode() and not self.has_lock():
            do_restart = functools.partial(self.while_not_sync_standby, do_restart)

        if run_async:
            self._async_executor.run_async(do_restart)
            return (True, 'restart initiated')
        else:
            res = self._async_executor.run(do_restart)
            if res:
                return (True, 'restarted successfully')
            elif res is None:
                return (False, 'postgres is still starting')
            else:
                return (False, 'restart failed')