from pydantic import BaseModel, Field

# Base schema
class LakeBase(BaseModel):
    name: str = Field(..., description="Name of the lake")
    location: str = Field(..., description="Location of the lake")
    description: str | None = Field(None, description="Description of the lake")

    class Config:
        schema_extra = {
            "example": {
                "name": "Lake Tahoe",
                "location": "California/Nevada, USA",
                "description": "A beautiful alpine lake on the California-Nevada border."
            }
        }

# Schema for creating a new Lake
class LakeCreate(LakeBase):
    pass

# Schema for Lake responses
class Lake(LakeBase):
    id: int
    name: str = Field(..., description="Name of the lake")
    location: str = Field(..., description="Location of the lake")
    description: str | None = Field(None, description="Description of the lake")

    class Config:
        orm_mode = True
        schema_extra = {
            "example": {
                "id": 1,
                "name": "Lake Tahoe",
                "location": "California/Nevada, USA",
                "description": "A beautiful alpine lake on the California-Nevada border."
            }
        }
```

This code defines three Pydantic models for the Lake entity:

1. `LakeBase`: A base model that defines the common fields for `name`, `location`, and `description`.
2. `LakeCreate`: A model that inherits from `LakeBase` and is used for creating a new Lake instance.
3. `Lake`: A model that inherits from `LakeBase` and includes an `id` field. This model is used for representing Lake instances in API responses.

The `LakeBase` model includes example values in its `Config` class, which can be used for documentation purposes.

The `Lake` model sets `orm_mode=True` in its `Config` class, which allows it to work with ORMs (Object-Relational Mappers) and handle reading data from a database. It also includes an example value for the `id` field.