chore: import upstream snapshot with attribution

docs-website/reference/experiments-api/experimental_chatmessage_store_api.md

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+---
+title: "ChatMessage Store"
+id: experimental-chatmessage-store-api
+description: "Storage for the chat messages."
+slug: "/experimental-chatmessage-store-api"
+---
+
+<a id="haystack_experimental.chat_message_stores.in_memory"></a>
+
+## Module haystack\_experimental.chat\_message\_stores.in\_memory
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore"></a>
+
+### InMemoryChatMessageStore
+
+Stores chat messages in-memory.
+
+The `chat_history_id` parameter is used as a unique identifier for each conversation or chat session.
+It acts as a namespace that isolates messages from different sessions. Each `chat_history_id` value corresponds to a
+separate list of `ChatMessage` objects stored in memory.
+
+Typical usage involves providing a unique `chat_history_id` (for example, a session ID or conversation ID)
+whenever you write, read, or delete messages. This ensures that chat messages from different
+conversations do not overlap.
+
+Usage example:
+```python
+from haystack.dataclasses import ChatMessage
+from haystack_experimental.chat_message_stores.in_memory import InMemoryChatMessageStore
+
+message_store = InMemoryChatMessageStore()
+
+messages = [
+    ChatMessage.from_assistant("Hello, how can I help you?"),
+    ChatMessage.from_user("Hi, I have a question about Python. What is a Protocol?"),
+]
+message_store.write_messages(chat_history_id="user_456_session_123", messages=messages)
+retrieved_messages = message_store.retrieve_messages(chat_history_id="user_456_session_123")
+
+print(retrieved_messages)
+```
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.__init__"></a>
+
+#### InMemoryChatMessageStore.\_\_init\_\_
+
+```python
+def __init__(skip_system_messages: bool = True,
+             last_k: int | None = 10) -> None
+```
+
+Create an InMemoryChatMessageStore.
+
+**Arguments**:
+
+- `skip_system_messages`: Whether to skip storing system messages. Defaults to True.
+- `last_k`: The number of last messages to retrieve. Defaults to 10 messages if not specified.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.to_dict"></a>
+
+#### InMemoryChatMessageStore.to\_dict
+
+```python
+def to_dict() -> dict[str, Any]
+```
+
+Serializes the component to a dictionary.
+
+**Returns**:
+
+Dictionary with serialized data.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.from_dict"></a>
+
+#### InMemoryChatMessageStore.from\_dict
+
+```python
+@classmethod
+def from_dict(cls, data: dict[str, Any]) -> "InMemoryChatMessageStore"
+```
+
+Deserializes the component from a dictionary.
+
+**Arguments**:
+
+- `data`: The dictionary to deserialize from.
+
+**Returns**:
+
+The deserialized component.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.count_messages"></a>
+
+#### InMemoryChatMessageStore.count\_messages
+
+```python
+def count_messages(chat_history_id: str) -> int
+```
+
+Returns the number of chat messages stored in this store.
+
+**Arguments**:
+
+- `chat_history_id`: The chat history id for which to count messages.
+
+**Returns**:
+
+The number of messages.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.write_messages"></a>
+
+#### InMemoryChatMessageStore.write\_messages
+
+```python
+def write_messages(chat_history_id: str, messages: list[ChatMessage]) -> int
+```
+
+Writes chat messages to the ChatMessageStore.
+
+**Arguments**:
+
+- `chat_history_id`: The chat history id under which to store the messages.
+- `messages`: A list of ChatMessages to write.
+
+**Raises**:
+
+- `ValueError`: If messages is not a list of ChatMessages.
+
+**Returns**:
+
+The number of messages written.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.retrieve_messages"></a>
+
+#### InMemoryChatMessageStore.retrieve\_messages
+
+```python
+def retrieve_messages(chat_history_id: str,
+                      last_k: int | None = None) -> list[ChatMessage]
+```
+
+Retrieves all stored chat messages.
+
+**Arguments**:
+
+- `chat_history_id`: The chat history id from which to retrieve messages.
+- `last_k`: The number of last messages to retrieve. If unspecified, the last_k parameter passed
+to the constructor will be used.
+
+**Raises**:
+
+- `ValueError`: If last_k is not None and is less than 0.
+
+**Returns**:
+
+A list of chat messages.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.delete_messages"></a>
+
+#### InMemoryChatMessageStore.delete\_messages
+
+```python
+def delete_messages(chat_history_id: str) -> None
+```
+
+Deletes all stored chat messages.
+
+**Arguments**:
+
+- `chat_history_id`: The chat history id from which to delete messages.
+
+<a id="haystack_experimental.chat_message_stores.in_memory.InMemoryChatMessageStore.delete_all_messages"></a>
+
+#### InMemoryChatMessageStore.delete\_all\_messages
+
+```python
+def delete_all_messages() -> None
+```
+
+Deletes all stored chat messages from all chat history ids.
+