This will train a neural network to produce a classifier for the classic "iris data set".
It's a fully connected neural network with three hidden layers (with 4, 3 and 2 neurons in those layers).
I wrote this while experimenting with F# and so it's written in a "functional" style (avoiding mutation) but by someone that is still getting to grips with it - so if some of the code looks odd or like it could be written in a clearer way then that is quite possibly the case!