getTransactions function Null safety

Future<TransactionBuilder> getTransactions(
  1. String address,
  2. String endpoint
)

Implementation

Future<TransactionBuilder> getTransactions(
    String address, String endpoint) async {
  final Completer<TransactionBuilder> _completer =
      Completer<TransactionBuilder>();
  TransactionBuilder? transactionChainResponse =
      new TransactionBuilder("keychain_access");

  final Map<String, String> requestHeaders = {
    'Content-type': 'application/json',
    'Accept': 'application/json',
  };

  String _body =
      '{"query":"query { transactionChain(address: \\"$address\\") {address, type, data { ledger { uco { transfers { amount, to } }, nft { transfers { amount, to, nft } } } } } }"}';
  print(_body);

  try {
    http.Response responseHttp = await http.post(Uri.parse(endpoint + '/api'),
        body: _body, headers: requestHeaders);
    print(responseHttp.body);

    if (responseHttp.statusCode == 200) {
      transactionChainResponse =
          transactionBuilderFromJson(responseHttp.body);
      /* if (transactionResponse.data != null &&
      transactionResponse.data!.transaction != null &&
      transactionResponse.data!.transaction!.data != null) {
        _content = transactionResponse.data!.transaction!.data!.content!;
      }*/
    }
  } catch (e) {
    print("error: " + e.toString());
  }

  _completer.complete(transactionChainResponse);
  return _completer.future;
}