Help using $watch()

[boustanihani]

I am using the alpine plugin alpine-autosize to resize textareas:
https://github.com/marcreichel/alpine-autosize/

I have an array of images [] inside Alpine.store('images').
Each image has some keywords that are displayed inside a textarea.

I am using x-for to display each image and its keywords.
I use :id because x-ref only accepts strings and not expressions.

My question is, how can I $watch for the keyword changes of a certain image?
I do not want all the textareas to autosize for performance reasons..
Please notice the question marks (??????) in my code =>

<template x-for="( image, index ) in $store.images">

    <textarea
        :id="'Keywords_'+index"
        x-model="image.keywords"
        x-init="$watch( ?????? , () => { $nextTick(() => { $autosize(document.getElementById('Keywords_'+index)); }); })"
    ></textarea>

</template>

[ekwoka]

image.keywords

[boustanihani]

Thanks