Defined in github.com/aws/aws-sdk-go/service/emr/api.go
To launch the job flow in Amazon Virtual Private Cloud (Amazon VPC), set this parameter to the identifier of the Amazon VPC subnet where you want the job flow to launch. If you do not specify this value, the job flow is launched in the normal Amazon Web Services cloud, outside of an Amazon VPC.
Amazon VPC currently does not support cluster compute quadruple extra large (cc1.4xlarge) instances. Thus you cannot specify the cc1.4xlarge instance type for nodes of a job flow launched in a Amazon VPC.