assertEquals(mygraph.numEdges(), 0);
mygraph.addEdges(sources, targets, edata);
assertEquals(mygraph.numEdges(), sources.size());
SimpleJsonFormatter formatter = new SimpleJsonFormatter();
String s = formatter.structWriter(mygraph).toString();
String expected = "{\"source\":1,\"targets\":[5]}\n"
+ "{\"source\":2,\"targets\":[4]}\n"
+ "{\"source\":3,\"targets\":[3]}\n"
+ "{\"source\":4,\"targets\":[2]}\n"
+ "{\"source\":5,\"targets\":[1]}\n";