title: How do you create a custom activation function with Keras?
body: <p>Sometimes the default <a href="https://keras.io/activations/" rel="noreferrer">standard activations</a> like ReLU, tanh, softmax, ... and the <a href="https://keras.io/layers/advanced-activations/" rel="noreferrer">advanced activations</a> like LeakyReLU aren't enough. And it might also not be in <a href="https://github.com/farizrahman4u/keras-contrib" rel="noreferrer">keras-contrib</a>.</p>
  
  <p>How do you create your own activation function?</p>