src/Tools/Graphview/src/mutator.scala

 {
   val name: String
   val description: String
   def mutate(complete: Model.Graph, sub: Model.Graph): Model.Graph
 
-  override def toString() = name
+  override def toString: String = name
 }
 
 trait Filter extends Mutator
 {
   def mutate(complete: Model.Graph, sub: Model.Graph) = filter(sub)