YouTube Subscription List API V3 [ unable to check subscribed user is still subscribed or not to my channel ]

I am using subscription/insert API to make user subscribe to my channel.

Responsedata{    kind:   "youtube#subscription"    etag:   "zNS9wkFH3YQT16N-f5BI8-bRK48"    id: "nSXLoI9bATpwVV8r7RGYlTiW3C3jrJ95s3ND0_KKkD8"    snippet{            publishedAt:    "2021-11-29T06:22:06.367041Z"        title:  "Jagadeesh Mekala"        description:    ""        resourceId{             kind:   "youtube#channel"            channelId:  "UCY4_uFTS5CsiLiNFTPagzqg"        }        channelId   "UC3KouvQ9tJwntWCWuDbBM9g"        thumbnails  {…}    }    status  200}

From the above response I am using snippet.channelId to check whether the user is subscribed or not.

POST:

https://www.googleapis.com/youtube/v3/subscriptions?part =snippet,contentDetails&key=apiKEY&forChannelId=UC3KouvQ9tJwntWCWuDbBM9g&mine=true

RESPONSE:

{"kind": "youtube#SubscriptionListResponse","etag": "qk1Tfs_Oukrn0Zd-vTvE13i0vIY","pageInfo": {"totalResults": 0,"resultsPerPage": 5    },"items": []}

If that first response's Response Channel id is subscribed it should return an array with details,but I got an empty array.

Are there any other methods to achieve this thing?