Fix ImportError caused by outdated "MessageContentText" and "ThreadMe…

…ssage" import

Updated the import statement to align with the new update in "openai.types.beta.threads", resolving the ImportError that prevented successful library usage.

llama-index-legacy/llama_index/legacy/agent/openai_assistant_agent.py

@@ -29,13 +29,13 @@
 
 def from_openai_thread_message(thread_message: Any) -> ChatMessage:
     """From OpenAI thread message."""
-    from openai.types.beta.threads import MessageContentText, ThreadMessage
+    from openai.types.beta.threads import TextContentBlock, Message
 
-    thread_message = cast(ThreadMessage, thread_message)
+    thread_message = cast(Message, thread_message)
 
     # we don't have a way of showing images, just do text for now
     text_contents = [
-        t for t in thread_message.content if isinstance(t, MessageContentText)
+        t for t in thread_message.content if isinstance(t, TextContentBlock)
     ]
     text_content_str = " ".join([t.text.value for t in text_contents])