Failed to validate dict when adding it as a new field in pydantic-redis example

I am learning pydantic-redis,and I tried to modify the example at https://github.com/sopherapps/pydantic-redis

by adding a new field new_field: dict = {} as follows

class Book(Model):
    _primary_key_field: str = 'title'
    title: str
    author: str
    published_on: date
    in_stock: bool = True
    new_field: dict = {}

when I run the example it says (in the end): value is not a valid dict (type=type_error.dict)

I have also tried other types, like new_field: List[int] = [8] (and then importing typing.List) On the other hand, when I add a new field with a primitive type like int, everything works fine.

What have I missed?

Best regards