How do I send metadata into a seperate Pydantic class?

I am parsing data from an API (https://rapidapi.com/apidojo/api/tasty, to be exact). I have two classes: Tip (represents a review on a recipe) and TipMetadata (represents all of the metadata associated with the Tip). I don't technically have to do this, but I prefer it this way. The problem is, when I get the data from the API, it isn't structured the same way I want it to be in my code.

Here is a simplified example to get my point across:

# tip.py

class Tip(BaseModel):
    author: str
    body: str
    metadata: TipMetadata

class TipMetadata(BaseModel):
    posted_at: datetime
    updated_at: datetime
    id: int

But here is what the data I am getting looks like:

{
    "author": "John Smith",
    "body": "Nice recipe!",
    "posted_at": 1716874324,
    "updated_at": 1716738295,
    "id": 8011
}

How do I make Pydantic parse posted_at, updated_at, and id into a TipMetadata object instead of ignoring them and complaining that there was no TipMetadata object in the data?

I've tried looking at the documentation and I found things called field_validator and custom types, but I feel like there is probably a simpler way to implement this and I just don't know what that is.

Edit:

I ended up doing the following:

class TipMetadata(BaseModel):
    posted_at: datetime
    updated_at: datetime
    id: int

class Tip(BaseModel):
    author: str
    body: str
    metadata: TipMetadata

    @pydantic.model_validator(mode="before")
    @classmethod
    def nest_metadata(
        cls, values: dict[str, typing.Any]
    ) -> typing.Dict[str, typing.Any]:
        metadata_fields = set(TipMetadata.model_fields)
        metadata_data = {
            key: values.pop(key) for key in metadata_fields if key in values
        }
        values["metadata"] = metadata_data
        return values

Solution

Devil's advocate - given that you're going to have to update the data models every time the API changes anyways, you might as well just define a hardcoded function that does that transformation for you. Assuming you've parsed the API response into a dict:

def response_to_classes(resp: dict) -> Tip:
    out = Tip(
        author = resp['author'],
        body = resp['body'],
        metadata = TipMetadata(
            posted_at = resp['posted_at'],
            updated_at = resp['updated_at'],
            id = resp['id']
        )
    )

    return out