How to reference two different collections of same db based on object_id in mongo and fastapi

Question

my schema for two collections.

class SectionModel(BaseModel):
    id: PyObjectId = Field(default_factory=PyObjectId, alias="_id")
    name: str = Field(max_length=50)

    class Config:
        allow_population_by_field_name = True
        arbitrary_types_allowed = True
        json_encoders = {ObjectId: str}
        schema_extra = {
            "example": {
                "name": "",
            }
        }


class FaqModel(BaseModel):
    id: PyObjectId = Field(default_factory=PyObjectId, alias="_id")
    section_id:str
    question:str = Field(max_length=50)
    answer:str = Field(max_length=100)

    class Config:
        allow_population_by_field_name = True
        arbitrary_types_allowed = True
        json_encoders = {ObjectId: str}
        schema_extra = {
            "example": {
                "section_id": "",
                "question": "",
                "answer": "",
            }
        }

my endpoint to create/add data

@router.post("/section",tags=["FAQ"])
def create_section(data: SectionModel = Body(...)):
     try:
         data = jsonable_encoder(data)
         new_section = crud.create_section(data=data)
         return {"success":True}

my crud method

def create_section(data):
   data = db["sections"].insert_one(data)
   return data

my db looks like this after adding data

db.sections.find().pretty();
    [
      {
        _id: '63e4a4d9304637ec1b578136',
        name: 'karnataka'
      },
      {
        _id: '63e4c2056f1845a3fc2180c5',
        name: 'Cricket'
      }
    ]
    
db.faqs.find().pretty();
    
    [
      {
        _id: '63e4cd7a1fdf5ee828bb33b9',
        section_id: '63e4a4d9304637ec1b578136',
        question: 'how many districts are in karnataka',
        answer: '31'
      },
      {
        _id: '63e4cd7a1fef5ee828c2b83b7',
        section_id: '63e4c2056f1845a3fc2180c5',
        question: 'who is called as hitman',
        answer: 'Rohit sharma'
      }
    ]

in faqs collection i am storing section_id as string and not referenced anywhere. if it is correct way then how to fetch response like,

{
    "section": ["karnataka", "Cricket"],
    "faq": {
        "karnataka": [{
            "question": "how many districts are in karnataka",
            "answer": "31"
        }, {
            "question": "q2",
            "answer": "ans2"
        }],
        "Cricket": [{
            "question": "who is called as hitman",
            "answer": "rohit sharma"
        }, {
            "question": "q4",
            "answer": "ans4"
        }]
    }
}

if not this way means how to reference from the model and achieve this. Thanks for input.