Given the root of a binary tree, display the values of its nodes while performing a level order traversal. Return the node values for all levels in a string separated by the character :. If the tree is empty, i.e., the number of nodes is $0$, then return “None” as the output.

Constraints:

• The number of nodes in the tree is in the range $[0, 500]$.

• $-10^3 \leq$ Node.data $\leq 10^3$

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in main.py in the following coding playground.

Note: The binary tree node’s class has members left and right to store references to other nodes, along with the member data to hold the node’s value.