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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 _enable_l1_keepalives(self, command):
 """ Enables L1 keepalive messages if supported. :param command: command line """


        env = os.environ.copy()
        if "IOURC" not in os.environ:
            env["IOURC"] = self.iourc_path
        try:
            output = yield from gns3server.utils.asyncio.subprocess_check_output(self._path, "-h", cwd=self.working_dir, env=env, stderr=True)
            if re.search("-l\s+Enable Layer 1 keepalive messages", output):
                command.extend(["-l"])
            else:
                raise IOUError("layer 1 keepalive messages are not supported by {}".format(os.path.basename(self._path)))
        except (OSError, subprocess.SubprocessError) as e:
            log.warning("could not determine if layer 1 keepalive messages are supported by {}: {}".format(os.path.basename(self._path), e))