The coax package doesn't include full-fledged agents. The reason is that it is designed for RL practitioners who want to create their own agents using a modular API.
For those who would like to have a starting point for creating pre-existing agents such as DQN or PPO we have collected simple Agent Stubs here. These stubs are partially complete python scripts that show the general structure of an agent.
sarsa qlearning soft_qlearning dqn dqn_per iqn
reinforce a2c ppo ddpg td3