如何在python中正确设置返回年份差值的函数？

from datetime import datetime

def get_year_difference(start_date, end_date):
    start_datetime = datetime.strptime(start_date, '%Y-%m-%d')
    end_datetime = datetime.strptime(end_date, '%Y-%m-%d')
    
    year_difference = end_datetime.year - start_datetime.year
    
    # 考虑起始日期的月份和日
    if (start_datetime.month, start_datetime.day) > (end_datetime.month, end_datetime.day):
        year_difference -= 1
    
    return year_difference

start_date = '1990-01-01'
end_date = '2022-12-31'

year_difference = get_year_difference(start_date, end_date)
print(year_difference)  # 输出 32