docs: function CallFunc (opts) {
      CallFunc.superclass.constructor.call(this, opts)
  
      // Save target & method so that copy() can recreate callback
      this.target = opts.target
      this.method = (typeof opts.method == 'function') ? opts.method : this.target[opts.method]
      this.callback = this.method.bind(this.target)
  }