Hub International organizes some policy coverage information as a rooted, n-ary tree. Each node contains an integer value and zero or more child nodes. Write a recursive function that returns the sum of values across the entire tree.
The tree is represented as nested Python dictionaries. Each node has a value key containing an integer and a children key containing a list of child-node dictionaries. An empty tree is represented by None and has sum 0.
Your implementation must visit every node exactly once. Values may be positive, zero, or negative. Explain how recursion uses the call stack, and identify the practical limitation when the tree is extremely deep.
Implement sum_coverage_tree(root), where root is either None or a dictionary with this shape:
{"value": int, "children": list[dict]}
Return one integer equal to the sum of every node value in the tree.
def sum_coverage_tree(root):