'Find all of the current instances that are running within this
security group.
:rtype: list of :class:`boto.ec2.instance.Instance`
:return: A list of Instance objects'

def instances(self, dry_run=False):

    rs = []
    if self.vpc_id:
        rs.extend(self.connection.get_all_reservations(filters={'instance.group-id': self.id}, dry_run=dry_run))
    else:
        rs.extend(self.connection.get_all_reservations(filters={'group-id': self.id}, dry_run=dry_run))
    instances = [i for r in rs for i in r.instances]
    return instances
