readCharacteristic method
Reads value of Characteristic matching specified UUIDs.
Returns value of characteristic with characteristicUuid for service with
serviceUuid. Optional transactionId could be used to cancel operation.
Will result in error if discovery was not done during this connection.
Implementation
Future<CharacteristicWithValue> readCharacteristic(
  String serviceUuid,
  String characteristicUuid, {
  String? transactionId,
}) =>
    _manager.readCharacteristicForDevice(
      this,
      serviceUuid,
      characteristicUuid,
      transactionId ?? TransactionIdGenerator.getNextId(),
    );