<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def to_text(self, fn:str):
        "Save `self.items` to `fn` in `self.path`."
        with open(self.path/fn, 'w') as f: f.writelines([f'{o}\n' for o in self._relative_item_paths()])