non-string fieldnames for csv.DictReader and csv.DictWriter - #5366

import csv
import enum
from typing import TYPE_CHECKING

class Foo(enum.Enum):
    X = 1
    Y = 2

def main() -> None:
    with open('foo.csv', 'w') as file:
        writer = csv.DictWriter(file, list(Foo))
        writer.writeheader()
        writer.writerow({Foo.X: "lol", Foo.Y: "wat"})

    with open('foo.csv', 'r') as file:
        foo_reader = csv.DictReader(file, list(Foo))
        print(list(foo_reader))
        if TYPE_CHECKING:
            reveal_type(next(foo_reader))

    with open('foo.csv', 'r') as file:
        string_reader = csv.DictReader(file)
        print(list(string_reader))
        if TYPE_CHECKING:
            reveal_type(next(string_reader))

main()