code: def update(self, validate=False):
          
          rs = self.connection.get_all_dbinstances(self.id)
          if len(rs) > 0:
              for i in rs:
                  if i.id == self.id:
                      self.__dict__.update(i.__dict__)
          elif validate:
              raise ValueError('%s is not a valid Instance ID' % self.id)
          return self.status
docs: Update the DB instance's status information by making a call to fetch
          the current instance attributes from the service.
  
          :type validate: bool
          :param validate: By default, if EC2 returns no data about the
                           instance the update method returns quietly.  If
                           the validate param is True, however, it will
                           raise a ValueError exception if no data is
                           returned from EC2.