Why is sign_transaction giving me this Error?

So the problem with my code is when i execute the signed_tx, it starts giving me errors, everything else works fine before that because i have printed everything and it is how it should be, so that is why i do not understand why does it suddenly give me the errors after that line.
As for the blockchain, i was using ganache, then i tried to use ganache-cli but still same errors.
I have tried looking a lot and changed a lot of settings but nothing seems to work.
Its my first time writing a question here, so forgive me if i am not detailed enough or made any mistake, thank you. really looking forward to solving this.

here is my code:

from solcx import compile_standard
import json
from web3 import Web3
import os
from dotenv import load_dotenv

load_dotenv()

with open("./SimpleStorage.sol", "r") as file:
    simple_storage_file = file.read()


Compiled_sol = compile_standard(
    {
        "language": "Solidity",
        "sources": {"SimpleStorage.sol": {"content": simple_storage_file}},
        "settings": {
            "outputSelection": {
                "*": {"*": ["abi", "metadata", "evm.bytecode", "evm.sourceMap"]}
            }
        },
    },
    solc_version="0.6.0",
)
with open("compiled_code.json", "w") as file:
    json.dump(Compiled_sol, file)

    # get Bytecode
    bytecode = Compiled_sol["contracts"]["SimpleStorage.sol"]["simpleStorage"]["evm"][
        "bytecode"
    ]["object"]

    # get abi
    abi = Compiled_sol["contracts"]["SimpleStorage.sol"]["simpleStorage"]["abi"]

    # for collecting to Ganache
    w3 = Web3(Web3.HTTPProvider("http://127.0.0.1:8545"))
    chain_id = "1337"
    my_address = "0x90F8bf6A479f320ead074411a4B0e7944Ea8c9C1"
    private_key = os.getenv("PK")
    # create the contract in python
    Simplestorage = w3.eth.contract(abi=abi, bytecode=bytecode)
    # get the nounce
    nonce = w3.eth.getTransactionCount(my_address)

    # 1: Build a Transaction
    # 2: Sign a Transaction
    # 3: Send a Transaction

    transaction = Simplestorage.constructor().buildTransaction(
        {
            "chainId": chain_id,
            "from": my_address,
            "nonce": nonce,
            "gasPrice": 20000000000,
            "gas": 6721975,
        }
    )
    print(transaction)
    signed_t = w3.eth.account.sign_transaction(transaction, private_key=private_key)```

here is the Error:

> Blockquote

Traceback (most recent call last):
  File "/Users/madscientist/demos/web3_py_simpleStorage/deploy.py", line 60, in <module>
    signed_t = w3.eth.account.sign_transaction(transaction, private_key=private_key)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/eth_utils/decorators.py", line 18, in _wrapper
    return self.method(obj, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/eth_account/account.py", line 748, in sign_transaction
    ) = sign_transaction_dict(account._key_obj, sanitized_transaction)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/eth_account/_utils/signing.py", line 32, in sign_transaction_dict
    unsigned_transaction = serializable_unsigned_transaction_from_dict(transaction_dict)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/eth_account/_utils/legacy_transactions.py", line 44, in serializable_unsigned_transaction_from_dict
    assert_valid_fields(transaction_dict)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/eth_account/_utils/legacy_transactions.py", line 109, in assert_valid_fields
    raise TypeError("Transaction had invalid fields: %r" % invalid)
TypeError: Transaction had invalid fields: {'chainId': '1337'}

> Blockquote