code: func (c *Cloud) findSecurityGroup(securityGroupID string) (*ec2.SecurityGroup, error) {
  	describeSecurityGroupsRequest := &ec2.DescribeSecurityGroupsInput{
  		GroupIds: []*string{&securityGroupID},
  	}
  	// We don't apply our tag filters because we are retrieving by ID
  
  	groups, err := c.ec2.DescribeSecurityGroups(describeSecurityGroupsRequest)
  	if err != nil {
  		glog.Warningf("Error retrieving security group: %q", err)
  		return nil, err
  	}
  
  	if len(groups) == 0 {
  		return nil, nil
  	}
  	if len(groups) != 1 {
  		// This should not be possible - ids should be unique
  		return nil, fmt.Errorf("multiple security groups found with same id %q", securityGroupID)
  	}
  	group := groups[0]
  	return group, nil
  }
docs: // Retrieves the specified security group from the AWS API, or returns nil if not found