initialize method
Implementation
Future<bool> initialize() async {
var anyOutputReadyCompleter = Completer<bool>();
setupStdout(_buildOutputStream(OutputStreamType.stdout, false,
_stdoutReadyFunction, anyOutputReadyCompleter));
setupStderr(_buildOutputStream(OutputStreamType.stderr, true,
_stderrReadyFunction, anyOutputReadyCompleter));
setupOutputReadyType(_outputReadyType);
return true;
}