Step $1$: Inspect the BSTNode.h and BinarySearchTree.h files

Inspect the BSTNode class declaration for a binary search tree node in BSTNode.h$.$ The BSTNode class has private member variables for the key, parent pointer, left child pointer, and right child pointer. Accessor functions exist for each.

Inspect the BinarySearchTree class declaration for a binary search tree in BinarySearchTree.h$.$ The GetNthKey$()$ function is the only pure virtual function that exists.