code: private SearchTree<VertexType> copySearchTree(SearchTree<VertexType> tree, Transpose<GraphType, EdgeType, VertexType> t) {
          // Copy this node
          SearchTree<VertexType> copy = new SearchTree<>(t.getOriginalGraphVertex(tree.getVertex()));
  
          // Copy children
          Iterator<SearchTree<VertexType>> i = tree.childIterator();
          while (i.hasNext()) {
              SearchTree<VertexType> child = i.next();
              copy.addChild(copySearchTree(child, t));
          }
  
          return copy;
      }
docs: Make a copy of given search tree (in the transposed graph) using vertices
  of the original graph.
  
  @param tree
  a search tree in the transposed graph
  @param t
  the Transpose object which performed the transposition of the
  original graph