code: def update(self, validate=False):
          
          rs = self.connection.get_all_instances([self.id])
          if len(rs) > 0:
              r = rs[0]
              for i in r.instances:
                  if i.id == self.id:
                      self._update(i)
          elif validate:
              raise ValueError('%s is not a valid Instance ID' % self.id)
          return self.state
docs: Update the instance's state 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.