class SlowCallGraph extends CallGraph {

  private final Set<Edge> edges = new HashSet<Edge>();
  private final MultiMap<Unit, Edge> unitMap = new HashMultiMap<Unit, Edge>();
  private final MultiMap<MethodOrMethodContext, Edge> srcMap = new HashMultiMap<MethodOrMethodContext, Edge>();
  private final MultiMap<MethodOrMethodContext, Edge> tgtMap = new HashMultiMap<MethodOrMethodContext, Edge>();
  private final ChunkedQueue<Edge> stream = new ChunkedQueue<Edge>();
  private final QueueReader<Edge> reader = stream.reader();

  /**
   * Used to add an edge to the call graph. Returns true iff the edge was not already present.
   */
  @Override
  public boolean addEdge(Edge e) {
    if (edges.add(e)) {
      stream.add(e);
      srcMap.put(e.getSrc(), e);
      tgtMap.put(e.getTgt(), e);
      unitMap.put(e.srcUnit(), e);
      return true;
    } else {
      return false;
    }
  }

  /**
   * Removes the edge e from the call graph. Returns true iff the edge was originally present in the call graph.
   */
  @Override
  public boolean removeEdge(Edge e) {
    if (edges.remove(e)) {
      srcMap.remove(e.getSrc(), e);
      tgtMap.remove(e.getTgt(), e);
      unitMap.remove(e.srcUnit(), e);
      return true;
    } else {
      return false;
    }
  }

  /**
   * Returns an iterator over all methods that are the sources of at least one edge.
   */
  @Override
  public Iterator<MethodOrMethodContext> sourceMethods() {
    return new ArrayList<MethodOrMethodContext>(srcMap.keySet()).iterator();
  }

  /**
   * Returns an iterator over all edges that have u as their source unit.
   */
  @Override
  public Iterator<Edge> edgesOutOf(Unit u) {
    return new ArrayList<Edge>(unitMap.get(u)).iterator();
  }

  /**
   * Returns an iterator over all edges that have m as their source method.
   */
  @Override
  public Iterator<Edge> edgesOutOf(MethodOrMethodContext m) {
    return new ArrayList<Edge>(srcMap.get(m)).iterator();
  }

  /**
   * Returns an iterator over all edges that have m as their target method.
   */
  @Override
  public Iterator<Edge> edgesInto(MethodOrMethodContext m) {
    return new ArrayList<Edge>(tgtMap.get(m)).iterator();
  }

  /**
   * Returns a QueueReader object containing all edges added so far, and which will be informed of any new edges that are
   * later added to the graph.
   */
  @Override
  public QueueReader<Edge> listener() {
    return (QueueReader<Edge>) reader.clone();
  }

  /**
   * Returns a QueueReader object which will contain ONLY NEW edges which will be added to the graph.
   */
  @Override
  public QueueReader<Edge> newListener() {
    return stream.reader();
  }

  @Override
  public String toString() {<FILL_FUNCTION_BODY>}

  /**
   * Returns the number of edges in the call graph.
   */
  @Override
  public int size() {
    return edges.size();
  }
}

    StringBuilder out = new StringBuilder();
    for (QueueReader<Edge> rdr = listener(); rdr.hasNext();) {
      Edge e = rdr.next();
      if (e != null) {
        out.append(e.toString()).append('\n');
      }
    }
    return out.toString();
  
<methods>public non-sealed void <init>() ,public boolean addEdge(soot.jimple.toolkits.callgraph.Edge) ,public Iterator<soot.jimple.toolkits.callgraph.Edge> edgesInto(soot.MethodOrMethodContext) ,public Iterator<soot.jimple.toolkits.callgraph.Edge> edgesOutOf(soot.Unit) ,public Iterator<soot.jimple.toolkits.callgraph.Edge> edgesOutOf(soot.MethodOrMethodContext) ,public soot.jimple.toolkits.callgraph.Edge findEdge(soot.Unit, soot.SootMethod) ,public boolean isEntryMethod(soot.SootMethod) ,public Iterator<soot.jimple.toolkits.callgraph.Edge> iterator() ,public QueueReader<soot.jimple.toolkits.callgraph.Edge> listener() ,public QueueReader<soot.jimple.toolkits.callgraph.Edge> newListener() ,public boolean removeAllEdgesOutOf(soot.Unit) ,public boolean removeEdge(soot.jimple.toolkits.callgraph.Edge) ,public boolean removeEdge(soot.jimple.toolkits.callgraph.Edge, boolean) ,public boolean removeEdges(Collection<soot.jimple.toolkits.callgraph.Edge>) ,public int size() ,public Iterator<soot.MethodOrMethodContext> sourceMethods() ,public boolean swapEdgesOutOf(soot.jimple.Stmt, soot.jimple.Stmt) ,public java.lang.String toString() <variables>protected soot.jimple.toolkits.callgraph.Edge dummy,protected Set<soot.jimple.toolkits.callgraph.Edge> edges,protected QueueReader<soot.jimple.toolkits.callgraph.Edge> reader,protected Map<soot.MethodOrMethodContext,soot.jimple.toolkits.callgraph.Edge> srcMethodToEdge,protected Map<soot.Unit,soot.jimple.toolkits.callgraph.Edge> srcUnitToEdge,protected ChunkedQueue<soot.jimple.toolkits.callgraph.Edge> stream,protected Map<soot.MethodOrMethodContext,soot.jimple.toolkits.callgraph.Edge> tgtToEdge