public void addToEquivalentMasks(ExportMask exportMask,ExportMaskPolicy policy){
  String key=generatePolicyKey(policy);
  Set<URI> similarMasks=equivalentMasks.get(key);
  if (similarMasks == null) {
    similarMasks=new HashSet<>();
    equivalentMasks.put(key,similarMasks);
  }
  similarMasks.add(exportMask.getId());
  exportMaskPolicy.put(exportMask.getId(),policy);
}

public void addToEquivalentMasks ( ExportMask exportMask , ExportMaskPolicy policy ) { String key = generatePolicyKey ( policy ) ; Set < URI > similarMasks = equivalentMasks . get ( key ) ; if ( similarMasks == null ) { similarMasks = new HashSet < > ( ) ; equivalentMasks . put ( key , similarMasks ) ; } similarMasks . add ( exportMask . getId ( ) ) ; exportMaskPolicy . put ( exportMask . getId ( ) , policy ) ; }
groups exportmask based on exportmaskpolicy equivalence ( minus the # volumes )
