How to use the jsrsasign.KEYUTIL.getKeyFromPlainPrivatePKCS8PEM function in jsrsasign

const decryptRemoteProposalResponse = (proposalResponseBytes64: string, eciesPrivateKeyPEM: any) => {
    const privKey = keyutil.getKeyFromPlainPrivatePKCS8PEM(eciesPrivateKeyPEM);
    const propResp = deserializeRemoteProposalResponseBase64(proposalResponseBytes64);
    const decryptionOptions = { hashAlgorithm: "SHA2" };
    //@ts-ignore Issue with propResp.payload not being a string but errors when converted to a string
    propResp.payload = eciesCrypto.eciesDecryptMessage(privKey, propResp.payload, decryptionOptions);
    return propResp;
};

const decryptRemoteChaincodeOutput = (proposalResponseBytes64, eciesPrivateKeyPEM) => {
    const privKey = keyutil.getKeyFromPlainPrivatePKCS8PEM(eciesPrivateKeyPEM);
    const propResp = deserializeRemoteProposalResponseBase64(proposalResponseBytes64);
    const decryptionOptions = { hashAlgorithm: "SHA2" };
    //@ts-ignore Issue with propResp.payload not being a string but errors when converted to a string
    propResp.response.payload = eciesCrypto.eciesDecryptMessage(privKey, propResp.response.payload, decryptionOptions);
    return propResp;
};