title: Reinforcement Learning with inputs of different sizes
body: <p>I am doing reinforcement learning with stable_baselines3 algorithms. The input size should vary between simulations (some simulations involve 4 objects that the agent receives information about, some have 9 objects, ...), but the size is fixed during all the steps of one given simulation.</p>
  <p>Is there a way for an agent to learn on simulations with different input sizes with stable_baselines algorithms (I am currently using PPO)? Otherwise what options do I have? I have read <a href="https://stable-baselines3.readthedocs.io/en/master/guide/custom_policy.html" rel="nofollow noreferrer">SB3's docs on custom policies</a> but could not understand if or how it answers my question.</p>