guides/making_new_layers_and_models_via_subclassing.py/MLPBlock/call
class MLPBlock:    def call(self, inputs):
        x = self.linear_1(inputs)
        x = keras.activations.relu(x)
        x = self.linear_2(x)
        x = keras.activations.relu(x)
        return self.linear_3(x)