This member is added by an implicit conversion from TarjanInformer[N] to
any2stringadd[TarjanInformer[N]] performed by method any2stringadd in scala.Predef.
This member is added by an implicit conversion from TarjanInformer[N] to
StringFormat[TarjanInformer[N]] performed by method StringFormat in scala.Predef.
Extended node visitor informer for Tarjan's algorithm.