Nitpick: Swift for TensorFlow currently is a fork of Swift, not a library implemented in Swift. https://github.com/tensorflow/swift:
”Compiler and standard library development happens on the tensorflow branch of the apple/swift repository.
[…]
Swift for TensorFlow is not intended to remain a long-term fork of the official Swift language. Language additions are designed to fit with the direction of Swift and will go through the Swift Evolution process.”