code: private void forceDecreaseKeyToMinimum(Node<K, V> n) {
          Node<K, V> y = n.parent;
          if (y != null) {
              cut(n, y);
              root.mark = false;
              cascadingRankChange(y);
              root = link(root, n);
          }
      }
docs: /*
  Decrease the key of a node to the minimum. Helper function for performing
  a delete operation. Does not change the node's actual key, but behaves as
  the key is the minimum key in the heap.