docs: function(fn, context, onDestroy){
        /** @cut */ var cursor = this;
        /** @cut */ while (cursor = cursor.handler)
        /** @cut */   if (cursor.fn === fn && cursor.context === context)
        /** @cut */     consoleMethods.warn('basis.Token#attach: duplicate fn & context pair');
  
        this.handler = {
          fn: fn,
          context: context,
          destroy: onDestroy || null,
          handler: this.handler
        };
      }