code: def subtract(self, years=0, months=0, weeks=0, days=0):
          
          return self.add(years=-years, months=-months, weeks=-weeks, days=-days)
docs: Remove duration from the instance.
  
          :param years: The number of years
          :type years: int
  
          :param months: The number of months
          :type months: int
  
          :param weeks: The number of weeks
          :type weeks: int
  
          :param days: The number of days
          :type days: int
  
          :rtype: Date