insertChild(index, node) {
    if (this.interceptHandler.appendChild) {
      const [_index, _node] = this.interceptHandler.insertChild.apply(
        this,
        arguments
      )
      if (typeof _index !== 'undefined') index = _index
      if (typeof _node !== 'undefined') node = _node
    }
    if (!TreeNode.isType(node)) {
      return false
    }
    if (this.isChecked) {
      node.setChecked(true)
    }
    node.parent = this
    this.childNodes.splice(index, 0, node)
    return true
  }
@param {number} index
@param {TreeNode} node