Reintroduce serialize_callback_handler and deserialize_callback_handler (#6988)

haystack/components/generators/utils.py

@@ -1,4 +1,7 @@
+from typing import Optional, Callable
+
 from haystack.dataclasses import StreamingChunk
+from haystack.utils.callable_serialization import serialize_callable, deserialize_callable
 
 
 def print_streaming_chunk(chunk: StreamingChunk) -> None:
@@ -7,3 +10,22 @@ def print_streaming_chunk(chunk: StreamingChunk) -> None:
     Prints the tokens of the first completion to stdout as soon as they are received
     """
     print(chunk.content, flush=True, end="")
+
+
+def serialize_callback_handler(streaming_callback: Callable[[StreamingChunk], None]) -> str:
+    """
+    Serializes the streaming callback handler.
+    :param streaming_callback: The streaming callback handler function
+    :return: The full path of the streaming callback handler function
+    """
+    return serialize_callable(streaming_callback)
+
+
+def deserialize_callback_handler(callback_name: str) -> Optional[Callable[[StreamingChunk], None]]:
+    """
+    Deserializes the streaming callback handler.
+    :param callback_name: The full path of the streaming callback handler function
+    :return: The streaming callback handler function
+    :raises DeserializationError: If the streaming callback handler function cannot be found
+    """
+    return deserialize_callable(callback_name)