function processBezierEasing(fn) {
  if (typeof fn === 'function') {
    return fn;
  } if (typeof (Easing[fn]) === 'function') {
    return Easing[fn];
  } if (/bezier/.test(fn)) {
    const bz = fn.replace(/bezier|\s|\(|\)/g, '').split(',');
    return new CubicBezier(bz[0] * 1, bz[1] * 1, bz[2] * 1, bz[3] * 1); // bezier easing
  }
  // if (/elastic|bounce/i.test(fn)) {
  //   throw TypeError(`KUTE - CubicBezier doesn't support ${fn} easing.`);
  // }
  return Easing.linear;
}
Returns a valid `easingFunction`.

@param {KUTE.easingFunction | string} fn function name or constructor name
@returns {KUTE.easingFunction} a valid easingfunction