Eye blink tracking

[Edgaras91]

I've been trying so hard to get this to work, but I (and Claude Opus 4.6) couldn't get it to work.
Can somebody give some guidance on how to get eye blink tracking to work? For me, in usually throws an exception at line:
_graph.WaitUntilIdle().AssertOk();

But Visual Studio can't understand it, so I can't see the message etc.
I am using "face_landmarks".
This is the GraphConfig (that Claude came up with):

    private const string GraphConfig = @"
input_stream: ""input_video""
output_stream: ""face_landmarks""

node {
  calculator: ""ConstantSidePacketCalculator""
  output_side_packet: ""PACKET:num_faces""
  node_options: {
    [type.googleapis.com/mediapipe.ConstantSidePacketCalculatorOptions]: {
      packet { int_value: 1 }
    }
  }
}

node {
  calculator: ""FaceLandmarkFrontCpu""
  input_stream: ""IMAGE:input_video""
  input_side_packet: ""NUM_FACES:num_faces""
  output_stream: ""LANDMARKS:multi_face_landmarks""
}

node {
  calculator: ""SplitNormalizedLandmarkListVectorCalculator""
  input_stream: ""multi_face_landmarks""
  output_stream: ""face_landmarks""
  node_options: {
    [type.googleapis.com/mediapipe.SplitVectorCalculatorOptions]: {
      ranges: { begin: 0 end: 1 }
      element_only: true
    }
  }
}
";
}