[Python] pymongo group by year based on subdocument date

I have mongodb document like

[
{
_id: ObjectId('67cfd69ba3e561d35ee57f51'),
created_at: ISODate('2025-03-11T06:22:19.044Z'),
conversation: [
{
id: '67cfd6c1a3e561d35ee57f53',
feedback: {
liked: false,
disliked: true,
copied: true,
created_at: ISODate('2025-03-11T06:27:48.634Z')
}
},
{
id: '67cfd77fa3e561d35ee57f54',
feedback: {
liked: true,
disliked: false,
copied: false,
created_at: ISODate('2025-03-11T06:28:25.099Z')
}
},
{ id: '67d009f1a3e561d35ee57f5a', feedback: null },
{ id: '67d009f8a3e561d35ee57f5b', feedback: null }
]
},
{
_id: ObjectId('67d00aeaa3e561d35ee57f5d'),
created_at: ISODate('2025-03-11T10:05:30.848Z'),
conversation: [
{ id: '67d00af7a3e561d35ee57f5f', feedback: null },
{ id: '67d00afaa3e561d35ee57f60', feedback: null }
]
}
]


Where main document has conversation sub document. I want to know how many likes, dislikes and copied data are there in each year.

I tried to get year from the conversation.feedback.created_at using $dateToString opeartor.

pipeline = [{'$match': {'conversation.feedback.copied': True}},
{'$group': {'_id': {'$dateToString': {'format': '%Y',
'date': '$conversation.feedback.created_at'}},
'total_copied': {'$sum': 1}}}]


but it gives error

OperationFailure: PlanExecutor error during aggregation :: caused by :: can't convert from BSON type array to Date, full error: {'ok': 0.0, 'errmsg': "PlanExecutor error during aggregation :: caused by :: can't convert from BSON type array to Date", 'code': 16006, 'codeName': 'Location16006'}


What I am expecting out as

{
"2025": {
"total_liked": 1,
"total_disliked": 1,
"total_copied": 1
}
}


How to convert the datetime object to Year and combine the total counts for 3 parameter?

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