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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 _get_persist_command(self):
 """Check availability and return path of command if available."""

        for command in [_SETSID_COMMAND, _NOHUP_COMMAND]:
            try:
                if command in self._adb.shell(['which',
                                               command]).decode('utf-8'):
                    return command
            except adb.AdbError:
                continue
        self.log.warning(
            'No %s and %s commands available to launch instrument '
            'persistently, tests that depend on UiAutomator and '
            'at the same time performs USB disconnection may fail',
            _SETSID_COMMAND, _NOHUP_COMMAND)
        return ''