[Python] pydantic get field alias based on field value with python object

I have pydantic model as below.

from typing import Annotated
from bson import ObjectId

from pydantic import Field
from pydantic import EmailStr
from pydantic import BaseModel
from pydantic import BeforeValidator
from pydantic import ConfigDict
from pydantic import AwareDatetime
from pydantic import field_validator

# Represents an ObjectId field in the database.
# It will be represented as a `str` on the model so that it can
# be serialized to JSON.
PyObjectId = Annotated[str, BeforeValidator(str)]

class DBTableBase(BaseModel):
# The primary key for the Table, stored as a `str` on the instance.
# This will be aliased to `_id` when sent to MongoDB,
# but provided as `id` in the API requests and responses.
id: PyObjectId | None = Field(alias="_id",
serialization_alias="id",
default=None)
model_config = ConfigDict(
json_encoders={ObjectId: str},
json_schema_extra={
"example": {
"id": "BSON_ID"
}
},
)

class ClientModel(DBTableBase):
first_name: str
last_name: str


I create object and print the model_dump

In [16]: a = ClientModel(_id=ObjectId(), first_name="first_name", last_name="last_name")

In [17]: a
Out[17]: ClientModel(id='67ce7b6190a330f1f5018315', first_name='first_name', last_name='last_name')

In [18]: a.model_dump()
Out[18]:
{'id': '67ce7b6190a330f1f5018315',
'first_name': 'first_name',
'last_name': 'last_name'}


This will convert _id of ObjectId to str as id in model_dump.

Is there any way to get it reverse like I pass id as str and will return _id as ObjectId?

In [19]: b = ClientModel(id='67ce7b6190a330f1f5018315', first_name='first_name', last_name='last_name')

In [20]: b.model_dump()
Out[20]: {'id': None, 'first_name': 'first_name', 'last_name': 'last_name'}

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