presto-geospatial-toolkit/src/main/java/io/prestosql/geospatial/KdbTree.java/KdbTree/getLeaves
class KdbTree:    public Map<Integer, Rectangle> getLeaves()
    {
        ImmutableMap.Builder<Integer, Rectangle> leaves = ImmutableMap.builder();
        addLeaves(root, leaves, node -> true);
        return leaves.build();
    }