Add stream

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

openai_chat.py

@@ -28,6 +28,7 @@ class OpenaiChat(PyOperator):
                  ):
         openai.api_key = os.getenv('OPENAI_API_KEY', api_key)
         self._model = model_name
+        self.stream = kwargs.pop('stream') if 'stream' in kwargs else False
         self.kwargs = kwargs
 
     def __call__(self, messages: List[dict]):
@@ -36,12 +37,11 @@ class OpenaiChat(PyOperator):
             model=self._model,
             messages=messages,
             n=1,
+            stream=self.stream,
             **self.kwargs
         )
-        if self.kwargs.get('stream'):
-            for chunk in response:
-                ans = chunk['choices'][0]['delta']
-                yield ans
+        if self.stream:
+            return self.stream_output(response)
         else:
             answer = response['choices'][0]['message']['content']
             return answer
@@ -65,6 +65,10 @@ class OpenaiChat(PyOperator):
                         'Invalid message key: only accept key value from ["system", "question", "answer"].'
                     new_messages.append(new_m)
         return new_messages
+    
+    def stream_output(self, response):
+        for resp in response:
+            yield resp['choices'][0]['delta']
 
     @staticmethod
     def supported_model_names():