Solidity Error: Identifier not found or not unique (UserOperation)

I'm encountering a compilation error in my Solidity code related to the UserOperation type. I'm using the BaseAccount contract from the account-abstraction library and trying to implement the _validateSignature function. However, the compiler throws an error saying "Identifier not found or not unique (UserOperation)".

Error (7920): Identifier not found or not unique.
   --> src/email-account/EmailAccount.sol:230:9:
    |
230 |         UserOperation calldata userOp,
    |         ^^^^^^^^^^^^^

Here's the relevant code snippet:

import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
import "@openzeppelin/contracts/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts/proxy/utils/UUPSUpgradeable.sol";

import "account-abstraction/core/BaseAccount.sol";
import "account-abstraction/core/Helpers.sol";
import "../callback/TokenCallbackHandler.sol";

import {Verifier} from "./Verifier.sol";
import "../utils/StringUtils.sol";

contract EmailAccount is
    BaseAccount,
    TokenCallbackHandler,
    UUPSUpgradeable,
    Initializable
{
/// implement template method of BaseAccount
    function _validateSignature(
        UserOperation calldata userOp,
        bytes32 userOpHash
    ) internal virtual override returns (uint256 validationData) {
        bytes32 hash = userOpHash.toEthSignedMessageHash();
        if (owner != hash.recover(userOp.signature))
            return SIG_VALIDATION_FAILED;
        return 0;
    }
}

Thank you in advance.

you are using variable UserOperation from one of the inherited classes. check those classes and most likely you are either using UserOperation wrong or it does not even exist.