code: func (t *EmpireTemplate) serviceRoleArn() interface{} {
  	if _, err := arn.Parse(t.ServiceRole); err == nil {
  		return t.ServiceRole
  	}
  	return Join("", "arn:aws:iam::", Ref("AWS::AccountId"), ":role/", t.ServiceRole)
  }
docs: // If the ServiceRole option is not an ARN, it will return a CloudFormation
  // expression that expands the ServiceRole to an ARN.