I tried to construct a graph using the method in LowLevelAPIExample.java.

```
BooleanEncodedValue accessEnc = VehicleAccess.create("car");
DecimalEncodedValue speedEnc = VehicleSpeed.create("car", 7, 2, false);
EncodingManager em = EncodingManager.start().add(accessEnc).add(speedEnc).build();
BaseGraph graph = new BaseGraph.Builder(em).setDir(new RAMDirectory(graphLocation, true)).create();
// Make a weighted edge between two nodes and set average speed to 50km/h
EdgeIteratorState edge = graph.edge(0, 1).setDistance(1234).set(speedEnc, 50);
// Set node coordinates and build location index
NodeAccess na = graph.getNodeAccess();
graph.edge(0, 1).set(accessEnc, true).set(speedEnc, 10).setDistance(1530);
na.setNode(0, 15.15, 20.20);
na.setNode(1, 15.25, 20.21);
```

But I found that the edges Iāv created have direction and the graph is a directed graph. How could I set the graph undirected or set the edges bidirectional?