supress ostringstream

src/graphRegex/GraphRegex.cpp

@@ -147,9 +147,7 @@ void GraphRegex::setNodeKey(const std::string key,std::function<bool(NodePtr)> f
     
     _majConditionalInterpreterLambda();
     //we add the lambda as key by default 
-    std::ostringstream oss;
-    oss << key << "($)==true";
-    setNodeKey(key, oss.str());
+    setNodeKey(key, key + "($)==true");
 }
 
 void GraphRegex::_majConditionalInterpreterLambda(){