Why all the schemas have a class with mixins and it's not used anywhere in the code

[Jkrox]

FastAPI-boilerplate/src/app/schemas/post.py

Lines 14 to 19 in fd11216

	class Post(TimestampSchema, PostBase, UUIDSchema, PersistentDeletion):
	media_url: Annotated[
	str | None,
	Field(pattern=r"^(https?|ftp)://[^\s/$.?#].[^\s]*$", examples=["https://www.postimageurl.com"], default=None),
	]
	created_by_user_id: int

FastAPI-boilerplate/src/app/schemas/rate_limit.py

Lines 23 to 25 in fd11216

	class RateLimit(TimestampSchema, RateLimitBase):
	tier_id: int
	name: Annotated[str | None, Field(default=None, examples=["users:5:60"])]

FastAPI-boilerplate/src/app/schemas/user.py

Lines 15 to 19 in fd11216

	class User(TimestampSchema, UserBase, UUIDSchema, PersistentDeletion):
	profile_image_url: Annotated[str, Field(default="https://www.profileimageurl.com")]
	hashed_password: str
	is_superuser: bool = False
	tier_id: int | None = None

what is the purpose for these schemas?

Newbie question because I'm starting to customize the code for my own purposes, but I can't get this unused stuff.