presto-geospatial-toolkit/src/main/java/io/prestosql/geospatial/KdbTree.java/KdbTree/split
class KdbTree:        @Override
        public SplitResult<Rectangle> split(Rectangle rectangle, double x)
        {
            checkArgument(rectangle.getXMin() < x && x < rectangle.getXMax());
            return new SplitResult<>(
                    new Rectangle(rectangle.getXMin(), rectangle.getYMin(), x, rectangle.getYMax()),
                    new Rectangle(x, rectangle.getYMin(), rectangle.getXMax(), rectangle.getYMax()));
        }