groupbyMapping.typename = subnodesRel.prototype;
groupbyMapping.typename = subnodesRel.groupbyprototype;
    public DbMapping getGroupbyMapping () {	if (subnodesRel == null || subnodesRel.groupby == null)	    return null;	if (groupbyMapping == null) {	    groupbyMapping = new DbMapping ();	    groupbyMapping.subnodesRel = subnodesRel.getGroupbySubnodeRelation ();	    if (propertiesRel != null)	        groupbyMapping.propertiesRel = propertiesRel.getGroupbyPropertyRelation ();	    else	        groupbyMapping.propertiesRel = subnodesRel.getGroupbyPropertyRelation ();	    groupbyMapping.typename = subnodesRel.prototype;	}	return groupbyMapping;    }