[RLlib] Unity3D integration (n Unity3D clients vs learning server). (#8590)

rllib/examples/env/multi_agent.py

@@ -4,12 +4,16 @@ from ray.rllib.env.multi_agent_env import MultiAgentEnv
 from ray.rllib.tests.test_rollout_worker import MockEnv, MockEnv2
 
 
-def make_multiagent(env_name):
+def make_multiagent(env_name_or_creator):
     class MultiEnv(MultiAgentEnv):
         def __init__(self, config):
-            self.agents = [
-                gym.make(env_name) for _ in range(config["num_agents"])
-            ]
+            num = config.pop("num_agents", 1)
+            if isinstance(env_name_or_creator, str):
+                self.agents = [
+                    gym.make(env_name_or_creator) for _ in range(num)
+                ]
+            else:
+                self.agents = [env_name_or_creator(config) for _ in range(num)]
             self.dones = set()
             self.observation_space = self.agents[0].observation_space
             self.action_space = self.agents[0].action_space