Function source_generator 

pub fn source_generator<F>(
    id: RString,
    factory: F,
    options: PluginOptions,
    runtime: PluginAsyncRuntimeObj,
    state_backend_config: PluginStateBackendConfig,
    message_channels: PluginChannels,
) -> RResult<PluginResult, PluginInitializationError>
where
    F: FnOnce(PluginAsyncRuntimeObj, PluginStateBackendFactory, PluginMetricsRecorder, HashMap<String, String>) -> Result<Arc<dyn SourcePlugin>, PluginInitializationError>,