code: private Node<K, V> get(Node<K, V> x, Interval1D<K> interval) {
      if (x == null) {
        return null;
      }
      int cmp = interval.compareTo(x.interval);
      if (cmp < 0) {
        return get(x.left, interval);
      } else if (cmp > 0) {
        return get(x.right, interval);
      } else {
        return x;
      }
    }
docs: Get the value associated with the given key (Interval). Interval must match exactly.
  
  @return null if no such key