revoke method
Implementation
Future<void> revoke(String privateKeyFrom, String credDidToRevoke) async {
var revokeFunction = _contract.function('revoke');
var tx = Transaction.callContract(
contract: _contract,
function: revokeFunction,
parameters: [_didToAddress(credDidToRevoke)]);
await web3Client.sendTransaction(EthPrivateKey.fromHex(privateKeyFrom), tx,
chainId: _chainId);
}