this idea of composing neural networks using a sequence of layers so whenever you have a sequential message passing system or sequentially processing information throughout the network you can use sequential models and just define your layers as a sequence and it's very nice to allow information to propagate through that model now if we want to create a deep neural network the idea is basically the same thing except you just keep stacking on more of these layers and to create more of an more of a hierarchical model ones where the