A bit of googling turns up [1][2], but [2] doesn't seem to have much recent activity (presumably in turn due to Google ceasing active development of S4TF [3]

[1] https://www.fast.ai/2019/03/06/fastai-swift/

[2] https://github.com/fastai/swiftai

[3] https://github.com/tensorflow/swift

Swift for Tensorflow was cancelled.