code: function nodeWalk(node, predicate, getChildNodes) {
    if (getChildNodes === void 0) {
      getChildNodes = module.exports.defaultChildNodes;
    }
    if (predicate(node)) {
      return node;
    }
    var match = null;
    var childNodes = getChildNodes(node);
    if (childNodes) {
      for (var i = 0; i < childNodes.length; i++) {
        match = nodeWalk(childNodes[i], predicate, getChildNodes);
        if (match) {
          break;
        }
      }
    }
    return match;
  }
docs: Walk the tree down from `node`, applying the `predicate` function.
  Return the first node that matches the given predicate.
  
  @returns `null` if no node matches, parse5 node object if a node matches.