fix: streamify should deepcopy settings before appending a callback

Author: glesperance

dspy/streaming/streamify.py

@@ -2,7 +2,9 @@
 import contextvars
 import logging
 import threading
+
 from asyncio import iscoroutinefunction
+from copy import deepcopy
 from queue import Queue
 from typing import TYPE_CHECKING, Any, AsyncGenerator, Awaitable, Callable, Generator
 
@@ -161,7 +163,7 @@ async def use_streaming():
     elif not iscoroutinefunction(program):
         program = asyncify(program)
 
-    callbacks = settings.callbacks
+    callbacks = deepcopy(settings.callbacks)
     status_streaming_callback = StatusStreamingCallback(status_message_provider)
     if not any(isinstance(c, StatusStreamingCallback) for c in callbacks):
         callbacks.append(status_streaming_callback)