code: function BezierBy (opts) {
      BezierBy.superclass.constructor.call(this, opts)
  
      this.config = util.copy(opts.bezier)
  }
docs: @class
  An action that moves the target with a cubic Bezier curve by a certain distance.
  
  @memberOf cocos.actions
  @extends cocos.actions.ActionInterval
  
  @opt {geometry.BezierConfig} bezier Bezier control points object
  @opt {Float} duration