Update README

Author: RussellLuo

README.md

@@ -73,19 +73,12 @@ from coagent.agents import StreamChatAgent, ChatMessage, ModelClient
 from coagent.core import AgentSpec, new, set_stderr_logger
 from coagent.runtimes import LocalRuntime
 
-client = ModelClient(
-    model=os.getenv("MODEL_NAME"),
-    api_base=os.getenv("MODEL_API_BASE"),
-    api_version=os.getenv("MODEL_API_VERSION"),
-    api_key=os.getenv("MODEL_API_KEY"),
-)
-
 translator = AgentSpec(
     "translator",
     new(
         StreamChatAgent,
         system="You are a professional translator that can translate Chinese to English.",
-        client=client,
+        client=ModelClient(model="openai/gpt-4o", api_key=os.getenv("OPENAI_API_KEY")),
     ),
 )
 
@@ -110,10 +103,7 @@ if __name__ == "__main__":
 Run the agent:
 
 ```bash
-export MODEL_NAME=<YOUR_MODEL_NAME>
-export MODEL_API_BASE=<YOUR_MODEL_API_BASE>
-export MODEL_API_VERSION=<YOUR_MODEL_API_VERSION>
-export MODEL_API_KEY=<YOUR_MODEL_API_KEY>
+export OPENAI_API_KEY="your-openai-key"
 python translator.py
 ```
 
@@ -138,19 +128,12 @@ from coagent.agents import StreamChatAgent, ModelClient
 from coagent.core import AgentSpec, idle_loop, new, set_stderr_logger
 from coagent.runtimes import NATSRuntime
 
-client = ModelClient(
-    model=os.getenv("MODEL_NAME"),
-    api_base=os.getenv("MODEL_API_BASE"),
-    api_version=os.getenv("MODEL_API_VERSION"),
-    api_key=os.getenv("MODEL_API_KEY"),
-)
-
 translator = AgentSpec(
     "translator",
     new(
         StreamChatAgent,
         system="You are a professional translator that can translate Chinese to English.",
-        client=client,
+        client=ModelClient(model="openai/gpt-4o", api_key=os.getenv("OPENAI_API_KEY")),
     ),
 )
 
@@ -169,10 +152,7 @@ if __name__ == "__main__":
 Run the agent as a daemon:
 
 ```bash
-export MODEL_NAME=<YOUR_MODEL_NAME>
-export MODEL_API_BASE=<YOUR_MODEL_API_BASE>
-export MODEL_API_VERSION=<YOUR_MODEL_API_VERSION>
-export MODEL_API_KEY=<YOUR_MODEL_API_KEY>
+export OPENAI_API_KEY="your-openai-key"
 python translator.py
 ```