(outerNode: OuterNode[OuterNode[NI]]).isDefined
(outerNode: OuterNode[OuterNode[NI]]).isEdge
(outerNode: OuterNode[OuterNode[NI]]).isIn
(outerNode: OuterNode[OuterNode[NI]]).isNode
(outerNode: OuterNode[OuterNode[NI]]).isOut
(outerNode: OuterNode[OuterNode[NI]]).stringPrefix
(outerNode: OuterNode[OuterNode[NI]]).toString()
(outerNode: OuterNode[OuterNode[NI]]).value
the type of the nodes (vertices) this graph is passed to by the user.