How do you use Keras LeakyReLU in Python?

All advanced activations in Keras, including LeakyReLU, are available as layers, and not as activations; therefore, you should use it as such:

from keras.layers import LeakyReLU

# instead of cnn_model.add(Activation('relu'))
# use
cnn_model.add(LeakyReLU(alpha=0.1))