from rl.agents.dqn import DQNAgent agent = DQNAgent(model=model, nb_actions=nb_actions, memory=memory, nb_steps_warmup=nb_steps_warmup, target_model_update=target_model_update) agent.compile(optimizer=optimizer, metrics=metrics)This code creates a DQNAgent object, specifying the neural network model to use, the number of possible actions, the memory object to store experience, the number of warmup steps before training, and the target model update frequency. The optimizer and metrics for training are also specified. One practical example of using DQNAgent could be to train an agent to play a videogame. The agent observes the current state of the game, selects an action to perform, and receives a reward. By repeating this process and updating the neural network, the agent can learn to perform better in the game. Overall, rl.agents.dqn is a package in the Keras-RL library, which provides reinforcement learning algorithms and environments for Python.