How to use the send2trash.compat.PY3 function in Send2Trash

def setUp(self):
        self.trashTopdir = mkdtemp(prefix='s2t')
        if PY3:
            trashTopdir_b = os.fsencode(self.trashTopdir)
        else:
            trashTopdir_b = self.trashTopdir
        self.fileName = 'test.txt'
        self.filePath = op.join(self.trashTopdir, self.fileName)
        touch(self.filePath)

        self.old_ismount = old_ismount = op.ismount
        self.old_getdev = send2trash.plat_other.get_dev
        def s_getdev(path):
            from send2trash.plat_other import is_parent
            st = os.lstat(path)
            if is_parent(self.trashTopdir, path):
                return 'dev'
            return st.st_dev
        def s_ismount(path):