The compilation process is required to link the layers in a model. The model.compile function requires the length of the inputs that will passed into the model as an argument. To compile a model, do the following

This will correctly compile the model, connecting the layers together and instantiating the parameters of the layer units.

Compiling a model, is the final step to creating a model. Now it is time to train your model on a dataset. Learn about training the model here.