orm_mode with PonyORM

[cschmatzler]

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Question

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.6.1
            pydantic compiled: False
                 install path: /home/christoph/.cache/pypoetry/virtualenvs/backend-WV529wjX-py3.8/lib/python3.8/site-packages/pydantic
               python version: 3.8.3 (default, May 13 2020, 19:59:26)  [GCC 9.2.0]
                     platform: Linux-5.4.67-x86_64-with-glibc2.2.5
     optional deps. installed: ['typing-extensions']

...

Unfortunately not self-contained because database setup required, but I hope my goal is obvious.
This should work as per Recursive ORM Models, but I am getting the following error:

pydantic.error_wrappers.ValidationError: 1 validation error for Organization
E           contents
E             value is not a valid list (type=type_error.list)

When querying ORMOrganization, ORMOrganization.contents is of type ORMOrganizationContentSet([ORMOrganizationContent[UUID('249941bf-fe64-430e-ae38-7731e60a9940')]]). Pony's content set doesn't seem to work for the recursive ORM mode? iter(contents) works, so I am not sure where to go from here.
Changing the type of Organization.contents to Set[OrganizationContent] does not change anything.

I searched the issues here for PonyORM and did not find anything. I would much appreciate any help regarding this!

import pydantic

# Database classes:

class ORMOrganization(database.Entity):
    id = PrimaryKey(UUID, default=uuid4, auto=True)
    contents = Set('ORMOrganizationContent', reverse="organization")


class ORMOrganizationContent(database.Entity):
    id = PrimaryKey(UUID, default=uuid4, auto=True)
    organization = Required("ORMOrganization")
    name = Required(str)

# Pydantic classes:
class OrganizationContent(pydantic.BaseModel):
    id: UUID
    name: str

    class Config:
        orm_mode = True


class Organization(pydantic.BaseModel):
    id: UUID
    contents: List[OrganizationContent]

    class Config:
        orm_mode = True

[layday]

I assume contents is an iterable which is neither a list nor is it sequence-like in Pydantic terms. I have no experience with Pony but the simplest thing to do here would be to use a validator.

[cschmatzler]

Thanks for the validator hint!
Adding

    @validator("contents", pre=True, allow_reuse=True)
    def pony_set_to_list(cls, v):
        return list(v)

solves my issue.

Thank you and have a great rest of your week!