code: public void setEc2SubnetIds(java.util.Collection<String> ec2SubnetIds) {
          if (ec2SubnetIds == null) {
              this.ec2SubnetIds = null;
              return;
          }
  
          this.ec2SubnetIds = new com.amazonaws.internal.SdkInternalList<String>(ec2SubnetIds);
      }
docs: <p>
  Applies to clusters that use the instance fleet configuration. When multiple EC2 subnet IDs are specified, Amazon
  EMR evaluates them and launches instances in the optimal subnet.
  </p>
  <note>
  <p>
  The instance fleet configuration is available only in Amazon EMR versions 4.8.0 and later, excluding 5.0.x
  versions.
  </p>
  </note>
  
  @param ec2SubnetIds
  Applies to clusters that use the instance fleet configuration. When multiple EC2 subnet IDs are specified,
  Amazon EMR evaluates them and launches instances in the optimal subnet.</p> <note>
  <p>
  The instance fleet configuration is available only in Amazon EMR versions 4.8.0 and later, excluding 5.0.x
  versions.
  </p>