Level Pair Sum in Binary Tree

Given a binary tree where each node contains an integer value, implement a function that processes the tree level by level. For every level, pair the nodes from the outermost ends inward:

• Pair the first node with the last node, the second node with the second last, and so on.
• If a level contains an odd number of nodes, the middle node remains unpaired and should be included as is.

Your function should return a list where each element represents a level in the tree and is itself a list of the computed sums for that level.

For example, consider the following binary tree:

       10
      /  \
     2    20
    / \   / \
   4   8 16  25

• Level 1: [10] → [10]
• Level 2: [2, 20] → [2 + 20] = [22]
• Level 3: [4, 8, 16, 25] → Pairs: (4, 25) and (8, 16) result in [29, 24]

Implement your solution in a programming language of your choice. You may assume the binary tree nodes are provided in a standard format (for example, a class with attributes for the node's value, left child, and right child).