<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_df(self)->None:
        "Create `pd.DataFrame` containing `items` from `self.x` and `self.y`."
        return pd.DataFrame(dict(x=self.x._relative_item_paths(), y=[str(o) for o in self.y]))