code: public void unfavorVirtualEdgePair(int virtualNodeId, int virtualEdgeId) {
          if (!isVirtualNode(virtualNodeId)) {
              throw new IllegalArgumentException("Node id " + virtualNodeId
                      + " must be a virtual node.");
          }
  
          VirtualEdgeIteratorState incomingEdge =
                  (VirtualEdgeIteratorState) getEdgeIteratorState(virtualEdgeId, virtualNodeId);
          VirtualEdgeIteratorState reverseEdge = (VirtualEdgeIteratorState) getEdgeIteratorState(
                  virtualEdgeId, incomingEdge.getBaseNode());
          incomingEdge.setUnfavored(true);
          unfavoredEdges.add(incomingEdge);
          reverseEdge.setUnfavored(true);
          unfavoredEdges.add(reverseEdge);
      }
docs: Sets the virtual edge with virtualEdgeId and its reverse edge to 'unfavored', which
  effectively penalizes both virtual edges towards an adjacent node of virtualNodeId.
  This makes it more likely (but does not guarantee) that the router chooses a route towards
  the other adjacent node of virtualNodeId.
  <p>
  
  @param virtualNodeId virtual node at which edges get unfavored
  @param virtualEdgeId this edge and the reverse virtual edge become unfavored