          pre_order_traversal(node, self.results.add_result)
          assert_equal(str(self.results), "[5, 2, 1, 3, 8]")
          self.results.clear_results()
  
          post_order_traversal(node, self.results.add_result)
          assert_equal(str(self.results), "[1, 3, 2, 8, 5]")
          self.results.clear_results()
  
          node = Node(1)
          insert(node, 2)
 
</s> remove         pre_order_traversal(node, self.results.add_result)
 </s> add         bst.pre_order_traversal(bst.root, self.results.add_result) </s> remove         node = Node(1)
        insert(node, 2)
        insert(node, 3)
        insert(node, 4)
        insert(node, 5)
 </s> add         bst = BstDfs(Node(1))
        bst.insert(2)
        bst.insert(3)
        bst.insert(4)
        bst.insert(5) </s> remove         in_order_traversal(node, self.results.add_result)
 </s> add         bst.in_order_traversal(bst.root, self.results.add_result) </s> remove         pre_order_traversal(node, self.results.add_result)
 </s> add         bst.pre_order_traversal(bst.root, self.results.add_result) </s> remove         post_order_traversal(node, self.results.add_result)
 </s> add         bst.post_order_traversal(bst.root, self.results.add_result)
        bst.post_order_traversal(bst.root, self.results.add_result)
          pre_order_traversal(node, self.results.add_result)
          assert_equal(str(self.results), "[5, 2, 1, 3, 8]")
          self.results.clear_results()
  
        bst.post_order_traversal(bst.root, self.results.add_result)
          assert_equal(str(self.results), "[1, 3, 2, 8, 5]")
          self.results.clear_results()
  
          node = Node(1)
          insert(node, 2)
keep keep keep keep replace keep keep keep keep keep
 Move tree dfs to a class 
graphs_trees/tree_dfs/test_dfs.py