code: @Override
      public void add(ImprintNode node) {
          Util.notNull(node, "Node");
          if (node.getLevel() != 0) {
              throw new IllegalArgumentException("ImprintNode with level greater than 0 is not supported by BlindingMaskLinkingHashTreeBuilder");
          }
          ImprintNode newNode = calculateNewNode(node);
          hashTreeBuilder.add(newNode);
          previousBlockHash = new DataHash(newNode.getValue());
      }
docs: Adds a new node to the tree.
  
  @param node a leaf to add to the tree, must not be null. The level of the node must be 0.
  @throws IllegalArgumentException if node level is greater than 0.