fitEnsemble cannot use "predict" method?

When I am using CrossVal or Holdout or CVPartition, The Predict method is not working and giving following error. How to use idss on SYS. Any idea ??

"Systems of classreg.learning.partition.ClassificationPartitionedEnsemble class cannot be used with the "predict" command. Convert the system to an identified model first, such as by using the "idss" command."