[Python] MongoEngine library doesn't allow to use its BaseFields for persisting data

I started to use mongoengine library in order to read and write data from Mongo DB.

I found some strage behavior. The following class is defined in my codebase:

class CustomerRequest(BaseModel):
type = fields.EnumField(RequestType)
status = fields.EnumField(Status, default=Status.NEW)
request_date = fields.DateField(db_field='requestDate')


I created an object of type CustomerRequest:

customer_request = CustomerRequest(type=Type.complaints, status=Status.Opened, request_date=DateTimeField("2023-03-01 00:00:00")


and then I persisted customer_request using mongoengine library:

customer_request.save()


After executing this line, I got the error:

Validation Failed: cannot parse date "<mongoengine.fields.datetimefield...>"
​

However, I found that if I create a CustomerRequest object with a "regular" datatime Python object:

customer_request = CustomerRequest(type=Type.complaints, status=Status.Opened, request_date=datetime("2023-03-01 00:00:00"))


Then, persistance goes well without any error.

I don't understand why CustomerRequest defines request_date as field of type DateTimeField, but expects this field to be of type datetime in order to persist it. Should I define two different classes for CustomerRequest? one that describes the data in the database, and a second that describes the object in Python code?

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