async def change_directory(self, path=".."):
        """
        :py:func:`asyncio.coroutine`

        Change current directory. Goes «up» if no parameters passed.

        :param path: new directory, goes «up» if omitted
        :type path: :py:class:`str` or :py:class:`pathlib.PurePosixPath`
        """
        path = pathlib.PurePosixPath(path)
        if path == pathlib.PurePosixPath(".."):
            cmd = "CDUP"
        else:
            cmd = "CWD " + str(path)
        await self.command(cmd, "2xx")
:py:func:`asyncio.coroutine`

        Change current directory. Goes «up» if no parameters passed.

        :param path: new directory, goes «up» if omitted
        :type path: :py:class:`str` or :py:class:`pathlib.PurePosixPath`