Program: 38790
Project: 38790
Buggy source:
public void exportTopology(OutputStream os) throws IOException {
  Graph g=new Graph().id("String_Node_Str" + NodeBreakerVoltageLevel.this.id + "String_Node_Str");
  Map<Integer,Node> intToNode=new HashMap<>();
  Multimap<String,Integer> busToNodes=ArrayListMultimap.create();
  for (int n=0; n < graph.getVertexCount(); n++) {
    Node node=new Node().id(Integer.toString(n));
    intToNode.put(n,node);
    Bus bus=getCalculatedBusBreakerTopology().getBus(n);
    if (bus != null) {
      busToNodes.put(bus.getId(),n);
    }
 else {
      TerminalExt terminal=graph.getVertexObject(n);
      if (terminal != null) {
        AbstractConnectable connectable=terminal.getConnectable();
        String label=n + "String_Node_Str" + connectable.getType().toString()+ "String_Node_Str"+ connectable.getId();
        node.attr("String_Node_Str",label);
        g.node(node);
      }
    }
  }
  String[] colors=Colors.generateColorScale(busToNodes.asMap().keySet().size());
  int i=0;
  for (  String key : busToNodes.asMap().keySet()) {
    Graph newBus=new Graph().id("String_Node_Str" + key + "String_Node_Str");
    newBus.attr("String_Node_Str",key);
    for (    int nodeInt : busToNodes.get(key)) {
      Node node=intToNode.get(nodeInt);
      TerminalExt terminal=graph.getVertexObject(nodeInt);
      if (terminal != null) {
        AbstractConnectable connectable=terminal.getConnectable();
        String label=nodeInt + "String_Node_Str" + connectable.getType().toString()+ "String_Node_Str"+ connectable.getId();
        node.attr("String_Node_Str",label);
      }
      node.attr("String_Node_Str","String_Node_Str").attr("String_Node_Str",colors[i]);
      newBus.node(node);
    }
    g.subGraph(newBus);
    i++;
  }
  boolean drawSwitchId=true;
  for (int e=0; e < graph.getEdgeCount(); e++) {
    Edge edge=new Edge(intToNode.get(graph.getEdgeVertex1(e)),intToNode.get(graph.getEdgeVertex2(e))).id(Integer.toString(e));
    SwitchImpl aSwitch=graph.getEdgeObject(e);
    if (aSwitch != null) {
      if (drawSwitchId) {
        edge.attr("String_Node_Str",aSwitch.getKind().toString() + "String_Node_Str" + aSwitch.getId()).attr("String_Node_Str","String_Node_Str");
      }
      edge.attr("String_Node_Str",aSwitch.isOpen() ? "String_Node_Str" : "String_Node_Str");
    }
    g.edge(edge);
  }
  g.writeTo(os);
}

Fixed version (ground truth):
public void exportTopology(OutputStream os){
  Graph g=new Graph().id("String_Node_Str" + NodeBreakerVoltageLevel.this.id + "String_Node_Str");
  Map<Integer,Node> intToNode=new HashMap<>();
  Multimap<String,Integer> busToNodes=ArrayListMultimap.create();
  for (int n=0; n < graph.getVertexCount(); n++) {
    Node node=new Node().id(Integer.toString(n));
    intToNode.put(n,node);
    Bus bus=getCalculatedBusBreakerTopology().getBus(n);
    if (bus != null) {
      busToNodes.put(bus.getId(),n);
    }
 else {
      TerminalExt terminal=graph.getVertexObject(n);
      if (terminal != null) {
        AbstractConnectable connectable=terminal.getConnectable();
        String label=n + "String_Node_Str" + connectable.getType().toString()+ "String_Node_Str"+ connectable.getId();
        node.attr(LABEL_ATTRIBUTE,label);
        g.node(node);
      }
    }
  }
  exportBuses(g,busToNodes,intToNode);
  exportEdges(g,intToNode);
  g.writeTo(os);
}