In NodeJS’s CommonJS module system, a module could only export one object: the one assigned to module.exports. The ES6 module system adds a new flavor of export on top of this, the default export. This allows you to both communicate the module’s primary function while still providing access to ancillary functions.
Keras is a favorite tool among many in Machine Learning. TensorFlow is even replacing their high level API with Keras come TensorFlow version 2. For those new to Keras. Keras is called a “front-end” api for machine learning. Using Keras you can swap out the “backend” between many frameworks in eluding TensorFlow, Theano, or CNTK officially.