[Python] FastAPI issues with MongoDB - TypeError: 'ObjectId' object is not iterable

I am having some issues inserting into MongoDB via FastAPI.

The below code works as expected. Notice how the response variable has not been used in response_to_mongo().

The model is an sklearn ElasticNet model.

app = FastAPI()


def response_to_mongo(r: dict):
client = pymongo.MongoClient("mongodb://mongo:27017")
db = client["models"]
model_collection = db["example-model"]
model_collection.insert_one(r)


@app.post("/predict")
async def predict_model(features: List[float]):

prediction = model.predict(
pd.DataFrame(
[features],
columns=model.feature_names_in_,
)
)

response = {"predictions": prediction.tolist()}
response_to_mongo(
{"predictions": prediction.tolist()},
)
return response


However when I write predict_model() like this and pass the response variable to response_to_mongo():

@app.post("/predict")
async def predict_model(features: List[float]):

prediction = model.predict(
pd.DataFrame(
[features],
columns=model.feature_names_in_,
)
)

response = {"predictions": prediction.tolist()}
response_to_mongo(
response,
)
return response


I get an error stating that:

TypeError: 'ObjectId' object is not iterable


From my reading, it seems that this is due to BSON/JSON issues between FastAPI and Mongo. However, why does it work in the first case when I do not use a variable? Is this due to the asynchronous nature of FastAPI?

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