code: function isPosterityNode(parent, child) {
    if (!isNode$2(parent) || !isNode$2(child)) {
      return false;
    }
    while (child.parentNode) {
      child = child.parentNode;
      if (child === parent) {
        return true;
      }
    }
    return false;
  }
docs: check if node B is node A's posterrity or not