Add usage code

README.md

@@ -23,6 +23,45 @@ model-index:
   # **DQN** Agent playing **LunarLander-v2**
   This is a trained model of a **DQN** agent playing **LunarLander-v2** using the [stable-baselines3 library](https://github.com/DLR-RM/stable-baselines3).
   
+## Usage (with Stable-Baselines3)
+  
+```python
+from huggingface_sb3 import load_from_hub
+from stable_baselines3 import DQN
+from stable_baselines3.common.env_util import make_vec_env
+from stable_baselines3.common.evaluation import evaluate_policy
+
+# Download checkpoint
+checkpoint = load_from_hub("araffin/dqn-LunarLander-v2", "dqn-LunarLander-v2.zip")
+# Remove warning
+kwargs = dict(target_update_interval=30)
+# Load the model
+model = DQN.load(checkpoint, **kwargs)
+
+env = make_vec_env("LunarLander-v2", n_envs=1)
+
+# Evaluate
+print("Evaluating model")
+mean_reward, std_reward = evaluate_policy(
+    model,
+    env,
+    n_eval_episodes=20,
+    deterministic=True,
+)
+print(f"Mean reward = {mean_reward:.2f} +/- {std_reward:.2f}")
+
+# Start a new episode
+obs = env.reset()
+
+try:
+    while True:
+        action, _states = model.predict(obs, deterministic=True)
+        obs, rewards, dones, info = env.step(action)
+        env.render()
+except KeyboardInterrupt:
+    pass
+```    
+    
   ## Training Code (with Stable-baselines3)
 
 ```python