Unable to use pydantic validators on Relation attributes #68

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Example Code

from sqlmodel import Field, Relationship, SQLModel

class Address(SQLModel, table=True):
    id: Optional[int] = Field(primary_key=True)
    country: str
    city: str
    street: str
    street_number: int

class Building(SQLModel, table=True):
    id: int = Field(primary_key=True)
    address_id: int = Field(foreign_key=f"{ADDRESSES}.id")
    address: Address = Relationship()
    age: int

    class Config:
        arbitrary_types_allowed = True

    @validator('address', pre=True)
    def validate_address(cls, v):
        return Address.parse_obj(v)

# Importing Building produces the error "pydantic.errors.ConfigError: Validators defined with incorrect fields: validate_address (use check_fields=False if you're inheriting from the model and intended this)"

Description

I want to parse a Building instance from a nested dictionary d with the Building and Address class defined in the example code.

d = {
  'address': {
     'country': 'US',
     'city': 'New York',
     'street': 'Centre St',
     'street_num': 1},
   'age': 40
}

So far I have been unavailable to successfully execute Building.parse_obj(d). Commenting out the validator in Building solves the pydantic error bein raised but the address of the parsed building will be a dict instead of an Address instance

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.4

Python Version

3.6.12

Additional Context

No response