description

# add method Null safety

Future add (

1. dynamic value,
2. [dynamic key]

)

## Implementation

    Future add(value, [key]) {
      try {
        var request;
        if (key != null) {
          request = _add(value, key);
        } else {
          request = _add(value);
        }
        return _completeRequest(request);
      } catch (e, stacktrace) {
        return new Future.error(e, stacktrace);
      }
    }