Q5: Cumulative Sum Write a function cumulative_sum that mutates the Tree t, where each node's label becomes the sum of all entries in the subtree rooted at the node. def cumulative_sum(t): "" "Mutates t where each node's root becomes the sum of all entries in the corresponding subtree rooted at t >>> t = Tree(1, [Tree(3, [Tree(5)]), Tree(7)]) >cumulative_sum(t) Tree(16, CTree(8, CTree(5)]), Tree(7)]) "*xYOUR CODE HERE" Use Ok to test your code