Set,
    Type,
    Union,
    cast,
)
from weakref import WeakKeyDictionary

import fastapi
from fastapi._compat import (
    PYDANTIC_V2,
    BaseConfig,
    ModelField,
    PydanticSchemaGenerationError,
    Undefined,
    UndefinedType,
    Validator,
    lenient_issubclass,
)
from fastapi.datastructures import DefaultPlaceholder, DefaultType
from pydantic import BaseModel, create_model