Nested Neural Networks

[helblazer811]

It would be nice to allow a user to pass a neural network into another neural network and have it be treated as a layer when constructing animations or renderings. It could look something like:

nested_network = NeuralNetwork([
     ImageLayer(),
     NeuralNetwork([
           Convolutional3DLayer(),
           Convolutional3DLayer(),
     ])
     FeedForwardLayer()
])

[helblazer811]

I think this would be a great way to implement certain custom layers like Transformer Self-Attention (#11) under the hood.