Added usage code

README.md

@@ -25,12 +25,31 @@ This is a trained model of a **PPO** agent playing **LunarLander-v2**
 using the [stable-baselines3 library](https://github.com/DLR-RM/stable-baselines3).
 
 ## Usage (with Stable-baselines3)
-TODO: Add your code
-
-
 ```python
-from stable_baselines3 import ...
+import gym
+from stable_baselines3 import PPO
+from stable_baselines3.common.evaluation import evaluate_policy
 from huggingface_sb3 import load_from_hub
 
-...
+repo_id = "yogeshkulkarni/ppo-LunarLander-v2" # The repo_id
+filename = "ppo-LunarLander-v2.zip" # The model filename.zip
+
+# When the model was trained on Python 3.8 the pickle protocol is 5
+# But Python 3.6, 3.7 use protocol 4
+# In order to get compatibility we need to:
+# 1. Install pickle5 (we done it at the beginning of the colab)
+# 2. Create a custom empty object we pass as parameter to PPO.load()
+custom_objects = {
+            "learning_rate": 0.0,
+            "lr_schedule": lambda _: 0.0,
+            "clip_range": lambda _: 0.0,
+}
+
+checkpoint = load_from_hub(repo_id, filename)
+model = PPO.load(checkpoint, custom_objects=custom_objects, print_system_info=True)
+
+# Evaluate this model
+eval_env = gym.make("LunarLander-v2")
+mean_reward, std_reward = evaluate_policy(model, eval_env, n_eval_episodes=10, deterministic=True)
+print(f"mean_reward={mean_reward:.2f} +/- {std_reward}")
 ```