docs: function bindParent (sticky) {
    if (!sticky instanceof Sticky) {
      return
    }
    const scroller = sticky.component.getParentScroller()
    let pt
    if (scroller) {
      pt = sticky.parent = scroller
      sticky.parentElement = pt.node
    }
    else {
      pt = sticky.parent = sticky.component.getRootContainer()
      sticky.parentElement = pt
    }
  }