Stack Traces Parser with Denoising

You are given a list of stack samples captured by a sampling profiler. Each sample is a tuple (timestamp, stack) where stack is a list of function names ordered from outermost to innermost. Consecutive samples often repeat the same stack prefix, so we compress the data into a tree: each node represents a function call and holds the total time it was on the stack (sum of sample deltas while it was present). After the tree is built, filter it with a duration threshold T. A node is kept if its total duration ≥ T OR any descendant is kept. Finally, print the surviving calls in a depth-first traversal with indentation proportional to depth.