code: def add_years(d, years_int):
          
  
          y, m, d = BaseDate.to_ymd(d)
          if not is_leap_year(years_int) and m == 2:
              d = min(28, d)
          return BaseDateFloat.from_ymd(y + years_int, m, d)
docs: adds number of years to a date
          :param BaseDateFloat d: date to add years to
          :param int years_int: number of years to add
          :return BaseDate: resulting date