this.$refs.lightbox.showImage is not a function

[snowtt]

I am using the example that contains the src / components / App.vue folder.

and I get an error called "this. $ refs.lightbox.showImage is not a function".
When activating: show-light-box = "true", it works fine for me, although I am looking to click on the image so that I am showing me the preview.

[MiguelRita]

<LightBox ref="referenceName"></LightBox>

 openGallery(index) {
      this.$refs.referenceName.showImage(index)
    }