from typing import List, Dict
from pydantic import BaseModel, ValidationError

class Pets(BaseModel):
    __root__: List[str]

    def __iter__(self):
        return iter(self.__root__)

    def __getitem__(self, item):
        return self.__root__[item]

pets = Pets.parse_obj(['dog', 'cat'])
print(pets[0])
print([pet for pet in pets])