LiveKit Flutter/Dart EGRESS support

Question

I am building a conferencing application making use of the Livekit SDK for Flutter & Dart. But I am unable to figure out how to setup the EGRESS functionality of Livekit in Dart.

EgressServiceClient client = EgressServiceClient.create(
        "http://example.com",
        "apiKey",
        "secret");


LivekitEgress.EncodedFileOutput output = LivekitEgress.EncodedFileOutput.newBuilder()
        .setFileType(LivekitEgress.EncodedFileType.MP4)
        .setFilepath("test-recording.mp4")
        .setS3(LivekitEgress.S3Upload.newBuilder()
                .setAccessKey("access-key")
                .setSecret("secret")
                .setBucket("bucket")
                .setEndpoint("https://my.s3.endpoint")
                .build())
        .build();

Call<LivekitEgress.EgressInfo> call = client.startRoomCompositeEgress(
        "roomName",
        output
);
try {
    LivekitEgress.EgressInfo egressInfo = call.execute().body();
    // handle engress info
} catch (IOException e) {
    // handle error
}

This is what is mentioned in the documentation of the Livekit.

But I am unable to find any function for the EGRESS setup like that in dart. I have already added livekit_client in my pubspec.yaml.