code: def add_years(self, datetimestr, n, return_date=False):
          
          a_datetime = self.parse_datetime(datetimestr)
  
          try:
              a_datetime = datetime(
                  a_datetime.year + n, a_datetime.month, a_datetime.day,
                  a_datetime.hour, a_datetime.minute,
                  a_datetime.second, a_datetime.microsecond)
          except:
              a_datetime = datetime(
                  a_datetime.year + n, 2, 28,
                  a_datetime.hour, a_datetime.minute,
                  a_datetime.second, a_datetime.microsecond)
  
          if return_date:
              return a_datetime.date()
          else:
              return a_datetime
docs: Returns a time that n years after a time.
  
          :param datetimestr: a datetime object or a datetime str
          :param n: number of years, value can be negative
          :param return_date: returns a date object instead of datetime
  
          **中文文档**
  
          返回给定日期N年之后的时间。