/** @see de.unika.ipd.grgen.ir.Expression#collectNeededEntities() */
 public void collectNeededEntities(NeededEntities needs) {
   needs.needsGraph();
   startNodeExpr.collectNeededEntities(needs);
   endNodeExpr.collectNeededEntities(needs);
   incidentEdgeTypeExpr.collectNeededEntities(needs);
   adjacentNodeTypeExpr.collectNeededEntities(needs);
 }