=== ray-project-0001: dag_node.py _get_toplevel_child_nodes O(A²) dedup ===
N=100   k=100  : defective=0.088ms  fixed=0.004ms  speedup=24.9x
N=500   k=500  : defective=2.166ms  fixed=0.020ms  speedup=105.8x
N=1000  k=1000 : defective=8.577ms  fixed=0.045ms  speedup=190.7x
N=2000  k=2000 : defective=34.711ms  fixed=0.096ms  speedup=359.8x

