code: private static boolean isTruePartitionOfTopLevelStep(Step step) {
  		Partition partition = step.getPartition();
  		
  		if (partition.getMapper() != null ) {
  			if (logger.isLoggable(Level.FINER)) {
  				logger.logp(Level.FINER, CLASSNAME, "validatePartition", "Found partitioned step with mapper" , step);
  			}
  			return true;
  		} else if (partition.getPlan() != null) {
  			if (partition.getPlan().getPartitions() != null) {
  				if (logger.isLoggable(Level.FINER)) {
  					logger.logp(Level.FINER, CLASSNAME, "validatePartition", "Found partitioned step with plan", step);
  				}
  			return true;
  			} else {
  				if (logger.isLoggable(Level.FINER)) {
  					logger.logp(Level.FINER, CLASSNAME, "validatePartition", "Found plan with partitions stripped out.  Must be a partition on the partition work unit thread", step);
  				}
  				return false;
  			}
  		} else {
  			throw new IllegalArgumentException("Partition does not contain either a mapper or a plan.  Aborting.");
  		}
  		
  	}
docs: Need to perform this check because of the way we manipulate the model in building our "subjob" for
  the partition.