from typing import Optional
from pydantic import BaseModel
from datetime import datetime

class PostBase(BaseModel):
    title: str
    content: str

class PostCreate(PostBase):
    pass

class PostUpdate(PostBase):
    pass

class PostInDBBase(PostBase):
    id: int
    created_at: datetime
    updated_at: Optional[datetime] = None

    class Config:
        orm_mode = True

class Post(PostInDBBase):
    pass

class PostList(BaseModel):
    __root__: list[Post]

Explanation:

1. We import the necessary modules: `typing` for type hints, `pydantic` for defining data models, and `datetime` for handling date and time.

2. `PostBase` is a base Pydantic model that defines the common fields for a post: `title` and `content`.



5. `PostInDBBase` inherits from `PostBase` and adds additional fields: `id` (post ID), `created_at` (creation timestamp), and `updated_at` (optional update timestamp). The `Config` class is set to `orm_mode = True` to allow Pydantic to work with SQLAlchemy models.




Make sure to install the required dependencies (`pydantic` and `sqlalchemy`) in your project environment if you haven't already done so.