### Undirected Graph Size

Create a public class named `GraphSize`

that provides a single static method `size`

.
`size`

receives an unweighted graph containing `Integer`

values using `cs1.graphs.UnweightedGraph`

, so an
`UnweightedGraph<Integer>`

.

To complete this problem you'll need to implement graph traversal.
From a given node, you want to visit all of its neighbors *except* any nodes that you've already visited.
If you use a `Set`

to track the nodes that you've visited, then you can simply return the size of that `Set`

when
you are finished.
We've provided some starter code to get you off on the right track.

For reference, `cs1.graphs.UnweightedGraph`

has the following public properties:

And `cs1.graphs.GraphNode`

has the following public properties: