code: function isInternalNode (node) {
    let tagName = (typeof node === 'string') ? node : node.tagName
    if (tagName && tagName.toLowerCase().indexOf('mip-i-') === 0) {
      return true
    }
  
    if (node.tagName && (node.hasAttribute('placeholder') ||
        node.hasAttribute('fallback') ||
        node.hasAttribute('overflow'))) {
      return true
    }
    return false
  }
docs: Returns "true" for internal MIP nodes or for placeholder elements.
  @param {!Node} node
  @return {boolean}