Question 3: Implement the following function: def restore_bst (prefix_lst) The function is given a listprefix_lst, which contains keys, given in an order that resulted from a prefix traversal of a binary search tree. When called, it creates and returns the binary search tree that when scanned in prefix order, it would give prefix_lst. For example, the call restore_bst ([9, 7, 3, 1, 5, 13, 11, 15]), should create and return the following tree: Notes: 1. The runtime of this function should be linear. 2. Assume that prefix_lst contains integers. 3. Assume that there are no duplicate values in prefix_lst. 4. You may want to define a helper function