presto-geospatial-toolkit/src/main/java/io/prestosql/geospatial/KdbTree.java/SplitResult/SplitResult
class SplitResult:        private SplitResult(T left, T right)
        {
            this.left = requireNonNull(left, "left is null");
            this.right = requireNonNull(right, "right is null");
        }