A model is a directed acyclic graph of layers.
keras_model(inputs, outputs = NULL)Input layer
Output layer
Other model functions: compile,
  evaluate_generator, evaluate,
  fit_generator, fit,
  get_config, get_layer,
  keras_model_sequential,
  pop_layer,
  predict.tensorflow.keras.engine.training.Model,
  predict_generator,
  predict_on_batch,
  predict_proba,
  summary.tensorflow.keras.engine.training.Model,
  train_on_batch