Add access to Links to AbstractExampleGraph

* Add method getBranchLink()
* Let method addEdge() return the created Link

src/test/java/org/mastodon/mamut/feature/branch/exampleGraph/AbstractExampleGraph.java

@@ -30,9 +30,11 @@
 
 import javax.annotation.Nonnull;
 
+import org.mastodon.mamut.model.Link;
 import org.mastodon.mamut.model.Model;
 import org.mastodon.mamut.model.ModelGraph;
 import org.mastodon.mamut.model.Spot;
+import org.mastodon.mamut.model.branch.BranchLink;
 import org.mastodon.mamut.model.branch.BranchSpot;
 import org.mastodon.mamut.model.branch.ModelBranchGraph;
 
@@ -70,6 +72,12 @@ public BranchSpot getBranchSpot(@Nonnull Spot spot)
 		return modelBranchGraph.getBranchVertex( spot, modelBranchGraph.vertexRef() );
 	}
 
+	public BranchLink getBranchLink( @Nonnull Link link )
+	{
+		rebuiltGraphIfRequired();
+		return modelBranchGraph.getBranchEdge( link, modelBranchGraph.edgeRef() );
+	}
+
 	private void rebuiltGraphIfRequired()
 	{
 		if ( ! branchGraphRequiresRebuild )
@@ -87,9 +95,10 @@ protected Spot addNode( @Nonnull String label, int timepoint, double[] xyz )
 		return spot;
 	}
 
-	protected void addEdge( @Nonnull Spot source, @Nonnull Spot target )
+	protected Link addEdge( @Nonnull Spot source, @Nonnull Spot target )
 	{
-		modelGraph.addEdge( source, target );
+		Link link = modelGraph.addEdge( source, target );
 		branchGraphRequiresRebuild = true;
+		return link;
 	}
 }