50    int insertLabelLayer( 
const QString &layerId, 
const QString &ruleId, 
const QSet<QgsSymbolLayerReference> &maskedSymbolLayers );
 
   56    int maskId( 
const QString &labelLayerId = QString(), 
const QString &labelRuleId = QString() ) 
const;
 
   68    QList<QSet<QgsSymbolLayerReference>> mLabelLayers;
 
   73    QList<QSet<QString>> mMaskIds;