Given a binary tree root. Split the binary tree into two subtrees by removing 1 edge such that the product of the sums of the subtrees are maximized. Since the answer may be too large, return it modulo 10^9 + 7. Example 1: Input: root = [1,2,3,4,5,6] Output: 110 Explanation: Remove the red edge and get 2 binary trees with sum 11 and 10. Their product is 110 (11*10) Example 2: Input: root = [1,null,2,3,4,null,null,5,6] Output: 90 Explanation: Remove the red edge and get 2 binary trees with sum 15 and 6.Their product is 90 (15*6) Example 3: Input: root = [2,3,9,10,7,8,6,5,4,11,1] Output: 1025 Example 4: Input: root = [1,1] Output: 1 Constraints: Each tree has at most 50000 nodes and at least 2 nodes. Each node's value is between [1, 10000].