chore: import upstream snapshot with attribution

docs-website/reference_versioned_docs/version-2.20/experiments-api/experimental_writers_api.md

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+---
+title: "Writers"
+id: experimental-writers-api
+description: "Writers for Haystack."
+slug: "/experimental-writers-api"
+---
+
+<a id="haystack_experimental.components.writers.chat_message_writer"></a>
+
+## Module haystack\_experimental.components.writers.chat\_message\_writer
+
+<a id="haystack_experimental.components.writers.chat_message_writer.ChatMessageWriter"></a>
+
+### ChatMessageWriter
+
+Writes chat messages to an underlying ChatMessageStore.
+
+Usage example:
+```python
+from haystack.dataclasses import ChatMessage
+from haystack_experimental.components.writers import ChatMessageWriter
+from haystack_experimental.chat_message_stores.in_memory import InMemoryChatMessageStore
+
+messages = [
+    ChatMessage.from_assistant("Hello, how can I help you?"),
+    ChatMessage.from_user("I have a question about Python."),
+]
+message_store = InMemoryChatMessageStore()
+writer = ChatMessageWriter(message_store)
+writer.run(chat_history_id="user_456_session_123", messages=messages)
+```
+
+<a id="haystack_experimental.components.writers.chat_message_writer.ChatMessageWriter.__init__"></a>
+
+#### ChatMessageWriter.\_\_init\_\_
+
+```python
+def __init__(chat_message_store: ChatMessageStore) -> None
+```
+
+Create a ChatMessageWriter component.
+
+**Arguments**:
+
+- `chat_message_store`: The ChatMessageStore where the chat messages are to be written.
+
+<a id="haystack_experimental.components.writers.chat_message_writer.ChatMessageWriter.to_dict"></a>
+
+#### ChatMessageWriter.to\_dict
+
+```python
+def to_dict() -> dict[str, Any]
+```
+
+Serializes the component to a dictionary.
+
+**Returns**:
+
+Dictionary with serialized data.
+
+<a id="haystack_experimental.components.writers.chat_message_writer.ChatMessageWriter.from_dict"></a>
+
+#### ChatMessageWriter.from\_dict
+
+```python
+@classmethod
+def from_dict(cls, data: dict[str, Any]) -> "ChatMessageWriter"
+```
+
+Deserializes the component from a dictionary.
+
+**Arguments**:
+
+- `data`: The dictionary to deserialize from.
+
+**Raises**:
+
+- `DeserializationError`: If the message store is not properly specified in the serialization data or its type cannot be imported.
+
+**Returns**:
+
+The deserialized component.
+
+<a id="haystack_experimental.components.writers.chat_message_writer.ChatMessageWriter.run"></a>
+
+#### ChatMessageWriter.run
+
+```python
+@component.output_types(messages_written=int)
+def run(chat_history_id: str, messages: list[ChatMessage]) -> dict[str, int]
+```
+
+Run the ChatMessageWriter on the given input data.
+
+**Arguments**:
+
+- `chat_history_id`: A unique identifier for the chat session or conversation whose messages should be retrieved.
+Each `chat_history_id` corresponds to a distinct chat history stored in the underlying ChatMessageStore.
+For example, use a session ID or conversation ID to isolate messages from different chat sessions.
+- `messages`: A list of chat messages to write to the store.
+
+**Returns**:
+
+- `messages_written`: Number of messages written to the ChatMessageStore.
+