Answer - Firstly, the Hyperparameters class is used for specifying a set of hyperparameters and their values, to be used in the model building function. Secondly, the Tuner subclasses corresponding to different tuning algorithms are called directly by the user to begin the search or to get the best models. Thirdly, the Oracle subclasses are the core search algorithms, receiving model evaluation results from the Tuner and providing new hyperparameter values. Lastly, the HyperModel subclasses are predefined search spaces for certain model families like ResNet and XceptionNet.