RawCborDecodeError when saving metadata in Cardano using Blockfrost Api

Question

I am trying to save metadata on Cardano using Blockfrost API, but I keep getting 400 error:

---

    {
        "error": "Bad Request",
        "message": '"transaction read error RawCborDecodeError [DecoderErrorDeserialiseFailure \\"Byron Tx\\" (DeserialiseFailure 0 \\"expected list len\\"),DecoderErrorDeserialiseFailure \\"Shelley Tx\\" (DeserialiseFailure 0 \\"expected list len or indef\\"),DecoderErrorDeserialiseFailure \\"Shelley Tx\\" (DeserialiseFailure 0 \\"expected list len or indef\\"),DecoderErrorDeserialiseFailure \\"Shelley Tx\\" (DeserialiseFailure 0 \\"expected list len or indef\\"),DecoderErrorDeserialiseFailure \\"Shelley Tx\\" (DeserialiseFailure 0 \\"expected list len or indef\\"),DecoderErrorDeserialiseFailure \\"Shelley Tx\\" (DeserialiseFailure 0 \\"expected list len or indef\\")]"',
        "status_code": 400,
    }

***.

However, I see that the transaction does submit on the blockfrost dashboard; I cannot figure out what I am missing.

  def frost_post(data_id, data):

    # Construct the payload for creating the transaction with metadata
    payload = {
        # "outputs": [
        #     {
        #         "address": receiving_address,
        #         # "amount": [{"unit": "lovelace", "quantity": 100000 }],
        #     }
        # ],
        "metadata": {data_id: {data_id: data}},
    }

    # testnet endpoint for creating a transaction with metadata
    url = "https://cardano-preprod.blockfrost.io/api/v0/tx/submit"

    # Headers including the API key
    headers = {
        "project_id": config('CARDANO_PROJECT_ID'),
        "Content-Type": "application/cbor",
    }

    # Make the POST request to create the transaction
    response = requests.post(url, headers=headers, data=cbor2.dumps(payload))

    # check if transaction is successful
    if response.status_code == 200:
        print("Transaction created successfully.")
    else:
        print(f"Transaction creation failed. Status code: {response.status_code}")

    # return response
    return response