build method
Implementation
FlagshipConfig build() {
return FlagshipConfig(_mode, _timeout, _pollingTime, _logLevel,
_onVisitorExposed, _trackingManagerConfig ?? TrackingManagerConfig(),
onSdkStatusChanged: _onSdkStatusChanged,
hitCacheImp: _hitCacheImp,
visitorCacheImp: _visitorCacheImp,
disableDeveloperUsageTracking: _disableDeveloperUsageTracking);
}