pydantest.py

from typing import ClassVar, Type, Dict, Generic, TypeVar, Any, List
from pydantic import BaseModel
#
T = TypeVar('T', bound=BaseModel)

class Response(BaseModel, Generic[T]):
    data: Type[BaseModel]
    metadata: Dict[str, Any]

    def __init__(self, *a, **kw) -> None:
        _metadata = kw.pop("metadata", {})
        _data = type(Type[T])(*a, **kw)
        super().__init__(data=_data, metadata=_metadata)

class X(BaseModel):
    """
    This class is the model used to answer to the client on the /parse route.
    """
    successes: List[str]
    failures: List[int]

class MyResponse(Response[X]):
    data: X

print(MyResponse(successes=["1","qsd"], failures=[3,4,5], metadata={"zzz": 133}).dict())

class Response(BaseModel):
    data: Type[BaseModel]
    metadata: Dict[str, Any]

    def __init__(self, *a, **kw) -> None:
        _metadata = kw.pop("metadata", {})
        _data_cls = self.__annotations__["data"]
        _data = _data_cls(*a, **kw)
        super().__init__(data=_data, metadata=_metadata)

class X(BaseModel):
    """
    This class is the model used to answer to the client on the /parse route.
    """
    successes: List[str]
    failures: List[int]