How to modify attributes of webhook object to algolia

Hi there !

I added Algolia search engine on my ghost blog(I referred ghost docs).
And my posts is trasferred to algolia index very well.

Currently, only title, headings, url, tags, authors, customRanking, slug, image, anchor attributes are transferred.
But I really want another attributes

So I tried to google, check ghost source codes, algolia node module code… but I didn’t find what to do…

How can I transfer another attributes of post to algolia index?
Please, help me