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main.py

from typing import Generic, TypeVar, Literal
from dataclasses import dataclass

T = TypeVar('T')

class RequestTypeToken(Generic[T]):
    """Token that proves a request type has been registered."""
    def __init__(self, type_name: T):
        self.name = type_name
        print(type(type_name))

@dataclass
class Request(Generic[T]):
    token: RequestTypeToken[T]
    # other fields...

class C:
    def __init__(self):
        self._registered_types: set[T] = set()
    
    def create_request_type(self, type_name: T) -> RequestTypeToken[T]:
        """Register a type and return a token."""
        self._registered_types.add(type_name)
        return RequestTypeToken(type_name)
    
    def send_request(self, request: Request) -> None:
        """Send a request - validates token is registered."""
        if request.token.name not in self._registered_types:
            raise ValueError(f"Type '{request.token.name}' not registered")
        print(f"Sending request of type: {request.token.name}")


# Usage
c = C()

# Register and get tokens
foo : Literal["foo"] = "foo"
foo_token = c.create_request_type(foo)

# Create requests with tokens
foo_req = Request(token=foo_token)
c.send_request(foo_req)
type(foo_token)