Define a recursive function named double_leaf_nodes (my_tree) which takes a binary tree as a parameter. The function doubles the value of the leaf nodes in the binary tree. This function updates the binary tree and it does not return anything. For example, the following binary tree: 42 (L) 21 (L) 1 (R) 2 (R) 65 (L) 5 (R) 9 The function updates the binary tree and the result is: 42 (L) 21 (L) 2 (R) 4 (R) 65 (L) 10 (R) 18 Note: - Submit the function in the answer box below assuming that the print_tree () function is given. Note: A BinaryTree implementation is provided to you as part of this exercise - you should not define your own BinaryTree class. Instead, your code can make use of any of the BinaryTree ADT attributes and methods. For example