保留数据类型的空 pandas 数据框

import pandas as pdimport datetimefrom dataclasses import dataclass@dataclassclass openorder:    symbol: str = "dummy"    sectype: str = "stk"    dt: datetime.datetime = datetime.datetime.now()    price: float = 0.0    status: str = none    def empty(self):        open_ord = self()        empty_df = pd.dataframe([open_ord.__dict__])        return empty_df.iloc[0:0]

open_order = OpenOrder()order_df = open_order.empty()

def empty(self):        empty_df = pd.DataFrame([self.__dict__])        return empty_df.iloc[0:0]