清除pandas dataframe列中不一致的日期格式

import pandas as pd
import re

data = {'日期': ['2021-01-01', '2021年1月2日', '2021/01/03', '2021-01-04']}
df = pd.DataFrame(data)

def convert_date_format(date):
    if re.match(r'\d{4}-\d{2}-\d{2}', date):
        return pd.to_datetime(date)
    elif re.match(r'\d{4}年\d{1,2}月\d{1,2}日', date):
        return pd.to_datetime(date, format='%Y年%m月%d日')
    elif re.match(r'\d{4}/\d{2}/\d{2}', date):
        return pd.to_datetime(date, format='%Y/%m/%d')
    else:
        return None

df['日期'] = df['日期'].apply(convert_date_format)

df.dropna(inplace=True)