How to use the airtest.utils.snippet.split_cmd function in airtest

def raw_shell(self, cmds, ensure_unicode=True):
        """
        Handle `adb shell` command(s) with unicode support

        Args:
            cmds: adb shell command(s)
            ensure_unicode: decode/encode unicode True or False, default is True

        Returns:
            command(s) output

        """
        cmds = ['shell'] + split_cmd(cmds)
        out = self.cmd(cmds, ensure_unicode=False)
        if not ensure_unicode:
            return out
        # use shell encoding to decode output
        try:
            return out.decode(self.SHELL_ENCODING)
        except UnicodeDecodeError:
            warnings.warn("shell output decode {} fail. repr={}".format(self.SHELL_ENCODING, repr(out)))
            return text_type(repr(out))

Raises:
            RuntimeError: if `device` is True and serialno is not specified

        Returns:
            a subprocess

        """
        if device:
            if not self.serialno:
                raise RuntimeError("please set serialno first")
            cmd_options = self.cmd_options + ['-s', self.serialno]
        else:
            cmd_options = self.cmd_options

        cmds = cmd_options + split_cmd(cmds)
        LOGGING.debug(" ".join(cmds))

        if not PY3:
            cmds = [c.encode(get_std_encoding(sys.stdin)) for c in cmds]

        proc = subprocess.Popen(
            cmds,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE
        )
        return proc

Run the `adb shell` command on the device

        Args:
            cmd: a command to be run

        Raises:
            AdbShellError: if command return value is non-zero or if any other `AdbError` occurred

        Returns:
            command output

        """
        if self.sdk_version < SDK_VERISON_NEW:
            # for sdk_version < 25, adb shell do not raise error
            # https://stackoverflow.com/questions/9379400/adb-error-codes
            cmd = split_cmd(cmd) + [";", "echo", "---$?---"]
            out = self.raw_shell(cmd).rstrip()
            m = re.match("(.*)---(\d+)---$", out, re.DOTALL)
            if not m:
                warnings.warn("return code not matched")
                stdout = out
                returncode = 0
            else:
                stdout = m.group(1)
                returncode = int(m.group(2))
            if returncode > 0:
                raise AdbShellError("", stdout)
            return stdout
        else:
            try:
                out = self.raw_shell(cmd)
            except AdbError as err: