An agent can now spawn an agent in AgentStep()

unity-environment/Assets/ML-Agents/Scripts/Brain.cs

 public enum StateType
 {
     discrete,
-    continuous}
+    continuous
+}
 ;
 
 
     }
 
 
-    public void CollectEverything() {
+    public void CollectEverything()
+    {
         currentStates.Clear();
         currentCameras.Clear();
         currentRewards.Clear();
     /// which are not done
     public void Step()
     {
-        foreach (Agent agent in agents.Values)
+        var agentsToIterate = agents.Values.ToList();
+        foreach (Agent agent in agentsToIterate)
         {
             if (!agent.done)
             {