I seem to have a compounded error

The first Error is I do not know How to do the sum aggregation with my data classes, I guess the serialization problem will go away once I have fixed it.

I have a Data Class(es)

data class MyClass(
    val items: List<Item>,
    val timestamp: Long = Instant.now().atOffset(ZoneOffset.UTC).toEpochSecond(),
    @BsonId
    val id: String = ObjectId().toString()
)

data class Item(
    val name: String,
    val price: Double,
    val qty: Double
)

I need to sum the price

MyClass::id = id

My Attempt

    override suspend fun sumPrice(id: String): Double {
        data class Result(val sumPrice: Double)
        return collection.aggregate<MyClass>(
            match(MyClass::id eq id),
            group(Result::sumPrice sum listOf(Item::price))
        ).first()?.sumPrice ?: 0.0
    }

This give me some problems

java.io.UncheckedIOException

Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.mongodb.client.model.SimpleExpression and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.mongodb.client.model.BsonField["value"])

I have tried this also, I am lost!

val result =  collection.aggregate<MyClass>(
    """[ { ${match()} : { _id: $ id } }, { $project: { _id: { 
        |$ sumPrice: { $sum: '$ items.price' } } } } ]""".trimMargin()
).first()?.sumPrice ?: 0.0

Please Assist and Teach me