[Python] Return all extra passed to pydantic model

I'm trying to get a list of all extra fields not defined in the schema. I saw solution posted here but it ignores any nested models. Optimal solution would create a variable in the Pydantic model with extras that I could access after new object with passed data is created but not sure if this is even possible.

Here is the code I'm working with.

Edit: I want .extras to be something like a property that returns not just the extra data directly on that instance, but also the extra data on any nested model instances it holds

from typing import Any, Dict, Optional
from pydantic import BaseModel
from pydantic import BaseModel, Field, root_validator

unnecessary_data = {
"name": "Lévy",
"age": 3,
"key_parent": "value", # unnecessary
"key2_parent": "value2", # unnecessary x2
"address": {
"city": "Wonderland",
"zip_code": "ABCDE",
"number": 123,
"key_child": 1232 # unnecessary x
}
}


class NewBase(BaseModel):
versio: Optional[str] = Field(alias='version') # just to show that it supports alias too
extra: Dict[str, Any]

@root_validator(pre=True)
def build_extra(cls, values: Dict[str, Any]) -> Dict[str, Any]:
all_required_field_names = {field.alias for field in cls.__fields__.values() if field.alias != 'extra'} # to support alias

extra: Dict[str, Any] = {}
for field_name in list(values):
if field_name not in all_required_field_names:
extra[field_name] = values.pop(field_name)
values['extra'] = extra
return values

class Address(NewBase):

"""
Cat API Address definition
"""
city: str
zip_code: str
number: int


class CatRequest(NewBase):
"""
Cat API Request definition
"""
name: str
age: int
address: Address


validated = CatRequest(**unnecessary_data)
print(validated.extras)
>> ["key_parent", "key2_parent", "address.key_child"]

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