code: function EaseRate (opts) {
      EaseRate.superclass.constructor.call(this, opts)
  
      this.rate = opts.rate
  }
docs: @class
  Base class for Easing actions with rate parameter
  
  @memberOf cocos.actions
  @extends cocos.actions.ActionEase
  
  @opt {cocos.actions.ActionInterval} action
  @opt {Float} rate