subclasses with SQLModel in FastAPI

Question

I'm writing classes for satellite components and need to specify dimensions. I've previously had the dimensions specified within the same class:

from sqlmodel import Field
from sqlmodel import SQLModel


class PropulsionSystemInput(SQLModel):
    """Propulsion system input class
    This class is used to validate the input data for the add_propulsion_system route.
    """

    name: str
    manufacturer: str
    date_of_development: str
    weight: float
    dimensions_x: float = Field(ge=0)
    dimensions_y: float = Field(ge=0)
    dimensions_z: float = Field(ge=0)
    power: float
    thrust: float
    fuel_type: str
    fuel_capacity: float
    fuel_consumption: float

Although this works, it isn't really functional and I defined a class:

from sqlmodel import SQLModel

class Dimensions(SQLModel):
    """Dimensions class
    This class is used to define the database table for dimensions.
    It adds an id field to the DimensionsInput class."""

    x: float
    y: float
    z: float

and updated the PropulsionSystemInput class to:

from sqlmodel import SQLModel
from backend.schemas.components.dimensions_schema import Dimensions

class PropulsionSystemInput(SQLModel):
    """Propulsion system input class
    This class is used to validate the input data for the add_propulsion_system route.
    """

    name: str
    manufacturer: str
    date_of_development: str
    weight: float
    dimensions: Dimensions
    power: float
    thrust: float
    fuel_type: str
    fuel_capacity: float
    fuel_consumption: float

However, when testing i get the following error: ValueError: The field dimensions has no matching SQLAlchemy type

I'm new to python and fastapi, so I googled, chatgpt'ed, copiloted and just couldn't get this to work.

I thought this question was pretty close to what I wanted to achieve, but somehow adapting it to my project didn't work.

Any help appreciated