How to change public policy of only one file in minio.io

I'm running local minio.io through docker.

I have the following structure.

Bucket: private

path: private / contract /

files:

• contract1.jpeg

• contract2.jpeg

individual path: private / contract / contract1.jpeg

I need to make available within the contract folder, only the contract1.jpeg for donwload. The other files should continue to be kept private.

I'm using sdk for javascript language. I tried to change the policy only from the file, but I only managed to change the 'policy' of the whole folder.

The link to minio documentation