EX$1$ Write a BST function named common$\_$ancestors that takes two values of templated type T as arguments:

DLList common$\_$ancestors$($const T & val$1,$ const T & val$2)$ const

The function should search the BST for these values and return a Doubly Linked List $($DLList$)$ containing the values of the common ancestors of val$1$ and val$2.$

Here's what the function should do in details:

If both val$1$ and val$2$ are found in the BST:

The function should return a DLList containing all the nodes that are ancestors of both val$1$ and val$2.$

If either val$1$ or val$2$ is not found in the BST:

The function should return an empty DLList The function should assume the BST has unique values for each node $($no duplicate values$).$

Note. You are not allowed to declare any additional data members, but you can define helper functions in the private section of the BST class. use only include string, do NOT use vector or any other STL