Getting error on the pydantic models : Input should be a valid dictionary or object to extract fields from

Question

I am trying to create the pydantic model for the post Api but i am getting the following error:

Input should be a valid dictionary or object to extract fields from

Could anyone please help me regarding this?

from typing import List

from fastapi import UploadFile, File, Form, Depends
from pydantic import BaseModel, Field


class Types(BaseModel):
    categoryid: str = Field()
    categoryname: str = Field()
    subcategoryid: str = Field()
    subcategoryname: str = Field()

    class Config:
        from_attributes = True
        populate_by_name = True
        arbitrary_types_allowed = False


class Availability(BaseModel):
    quantity: int = Form(...)
    size: str = Form(...)
    price: str = Form(...)

    class Config:
        from_attributes = True
        populate_by_name = True
        arbitrary_types_allowed = False


class ProductUnits(BaseModel):
    color: str = Form(...)
    image: str = Form(...)
    # availability: List[Availability] = Depends()


class Product(BaseModel):
    # productname: Optional[str] = None
    # minorder: Optional[int] = None
    # producttype: Types = Depends()
    # productdetails: Optional[str] = None
    productunits: List[ProductUnits]
    # shippingtime: Optional[str] = None
    # cod: Optional[bool] = None
    # codminimumamt: Optional[int] = None
    # returnpolicy: Optional[str] = None
    productimages: list[UploadFile] = File(...)

Router

from fastapi import APIRouter, Request, status, Depends

from src.products.models import Product
from src.utils.statuscode import statuscode

productrouter = APIRouter()


@productrouter.post("/", response_description="Create a products", status_code=status.HTTP_201_CREATED,
                    )
async def create_product(request: Request, product: Product = Depends()):
    print(product)
    return statuscode(status=True, message='Product added Successfully')

Error Track

    {
  "detail": [
    {
      "type": "model_attributes_type",
      "loc": [
        "body",
        "productunits",
        0
      ],
      "msg": "Input should be a valid dictionary or object to extract fields from",
      "input": "{\r\n  \"color\": \"string\",\r\n  \"image\": \"string\"\r\n}",
      "url": "https://errors.pydantic.dev/2.4/v/model_attributes_type"
    }
  ]
}

I had tried to change the typing values and base model many more but i able achieve the expected output

Please help me understand whats the issue causing that error in the pydantic when i try to run that api