[Python] how to make all field optional with alias name?

I am following https://stackoverflow.com/a/77851176/243031 to create my model optional.

I created function to get base class annotations.

def get_annotations(main_cls):
ret_val = main_cls.__annotations__
for base_cls in main_cls.__bases__:
if base_cls != BaseModel:
ret_val.update(get_annotations(base_cls))
return ret_val


and created optional model as

OptionalClientModel = create_model(
"OptionalClientModel",
**{k: (Optional[v], None) for k, v in get_annotations(ClientModel).items()})


The original classes are 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 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


When I want model with all optional value, I can use OptionalClientModel.

The issue is, id in OptionalClientModel has no alias.

How to create optional with alias?

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