code: function getChildBeforeLoad(animate, child, data, cb) {
    animate = assign({}, animate, { onEnd: cb });
    if (animate && animate.onLoad && !animate.onLoad.duration) {
      return { animate, data };
    }
    const before = animate.onLoad && animate.onLoad.before ? animate.onLoad.before : identity;
    // If nodes need to exit, transform them with the provided onLoad.before function.
    data = data.map((datum, idx) => {
      return assign({}, datum, before(datum, idx, data));
    });
  
    return { animate, data, clipWidth: 0 };
  }
docs: eslint-disable-next-line max-params