code: def check_dates(self):
          '''
          This method is used to validate the checkin_date and checkout_date.
          -------------------------------------------------------------------
          @param self: object pointer
          @return: raise warning depending on the validation
          '''
          if self.checkin_date >= self.checkout_date:
                  raise ValidationError(_('Room line Check In Date Should be \
                  less than the Check Out Date!'))
          if self.folio_id.date_order and self.checkin_date:
              if self.checkin_date <= self.folio_id.date_order:
                  raise ValidationError(_('Room line check in date should be \
                  greater than the current date.')f check_dates(self):
          '''
          This method is used to validate the checkin_date and checkout_date.
          -------------------------------------------------------------------
          @param self: object pointer
          @return: raise warning depending on the validation
          '''
          if self.checkin_date >= self.checkout_date:
                  raise ValidationError(_('Room line Check In Date Should be \
                  less than the Check Out Date!'))
          if self.folio_id.date_order and self.checkin_date:
              if self.checkin_date <= self.folio_id.date_order:
                  raise ValidationError(_('Room line check in date should be \
                  greater than the current date.'))
docs: This method is used to validate the checkin_date and checkout_date.
          -------------------------------------------------------------------
          @param self: object pointer
          @return: raise warning depending on the validation