[K-means clustering](https://github.com/dotnet/machinelearning/tree/86f5ee663611f6c97ddb87be1150601018d74b4b/src/Microsoft.ML.KMeansClustering) is already available as a learner in ML.NET, but it is not exposed in the APIs and cannot be used in `LearningPipeline`. The entry point needs to be added to the C# APIs (along with other necessary components like the clustering evaluator).