How to use the pynvim.api.common.walk function in pynvim

def filter_notification_cb(name, args):
            name = self._from_nvim(name)
            args = walk(self._from_nvim, args)
            try:
                notification_cb(name, args)
            except Exception:
                msg = ("error caught in notification handler '{} {}'\n{}\n\n"
                       .format(name, args, format_exc_skip(1)))
                self._err_cb(msg)
                raise

"""
        if (self._session._loop_thread is not None
                and threading.current_thread() != self._session._loop_thread):

            msg = ("Request from non-main thread.\n"
                   "Requests from different threads should be wrapped "
                   "with nvim.async_call(cb, ...) \n{}\n"
                   .format('\n'.join(format_stack(None, 5)[:-1])))

            self.async_call(self._err_cb, msg)
            raise NvimError("request from non-main thread")

        decode = kwargs.pop('decode', self._decode)
        args = walk(self._to_nvim, args)
        res = self._session.request(name, *args, **kwargs)
        return walk(self._from_nvim, res, decode=decode)

def next_message(self):
        """Block until a message(request or notification) is available.

        If any messages were previously enqueued, return the first in queue.
        If not, run the event loop until one is received.
        """
        msg = self._session.next_message()
        if msg:
            return walk(self._from_nvim, msg)

present and True, a asynchronous notification is sent instead. This
        will never block, and the return value or error is ignored.
        """
        if (self._session._loop_thread is not None
                and threading.current_thread() != self._session._loop_thread):

            msg = ("Request from non-main thread.\n"
                   "Requests from different threads should be wrapped "
                   "with nvim.async_call(cb, ...) \n{}\n"
                   .format('\n'.join(format_stack(None, 5)[:-1])))

            self.async_call(self._err_cb, msg)
            raise NvimError("request from non-main thread")

        decode = kwargs.pop('decode', self._decode)
        args = walk(self._to_nvim, args)
        res = self._session.request(name, *args, **kwargs)
        return walk(self._from_nvim, res, decode=decode)

def filter_request_cb(name, args):
            name = self._from_nvim(name)
            args = walk(self._from_nvim, args)
            try:
                result = request_cb(name, args)
            except Exception:
                msg = ("error caught in request handler '{} {}'\n{}\n\n"
                       .format(name, args, format_exc_skip(1)))
                self._err_cb(msg)
                raise
            return walk(self._to_nvim, result)

def filter_request_cb(name, args):
            name = self._from_nvim(name)
            args = walk(self._from_nvim, args)
            try:
                result = request_cb(name, args)
            except Exception:
                msg = ("error caught in request handler '{} {}'\n{}\n\n"
                       .format(name, args, format_exc_skip(1)))
                self._err_cb(msg)
                raise
            return walk(self._to_nvim, result)