community[minor]: Relax constraints on CassandraChatMessageHistory constructor (#21241)

libs/community/langchain_community/chat_message_histories/cassandra.py

@@ -2,11 +2,10 @@
 from __future__ import annotations
 
 import json
-import typing
 import uuid
-from typing import List
+from typing import TYPE_CHECKING, List, Optional
 
-if typing.TYPE_CHECKING:
+if TYPE_CHECKING:
     from cassandra.cluster import Session
 
 from langchain_core.chat_history import BaseChatMessageHistory
@@ -26,8 +25,8 @@ class CassandraChatMessageHistory(BaseChatMessageHistory):
     Args:
         session_id: arbitrary key that is used to store the messages
             of a single chat session.
-        session: a Cassandra `Session` object (an open DB connection)
-        keyspace: name of the keyspace to use.
+        session: Cassandra driver session. If not provided, it is resolved from cassio.
+        keyspace: Cassandra key space. If not provided, it is resolved from cassio.
         table_name: name of the table to use.
         ttl_seconds: time-to-live (seconds) for automatic expiration
             of stored entries. None (default) for no expiration.
@@ -36,10 +35,10 @@ class CassandraChatMessageHistory(BaseChatMessageHistory):
     def __init__(
         self,
         session_id: str,
-        session: Session,
-        keyspace: str,
+        session: Optional[Session] = None,
+        keyspace: Optional[str] = None,
         table_name: str = DEFAULT_TABLE_NAME,
-        ttl_seconds: typing.Optional[int] = DEFAULT_TTL_SECONDS,
+        ttl_seconds: Optional[int] = DEFAULT_TTL_SECONDS,
     ) -> None:
         try:
             from cassio.table import ClusteredCassandraTable
@@ -74,7 +73,11 @@ class CassandraChatMessageHistory(BaseChatMessageHistory):
         return messages
 
     def add_message(self, message: BaseMessage) -> None:
-        """Write a message to the table"""
+        """Write a message to the table
+
+        Args:
+            message: A message to write.
+        """
         this_row_id = uuid.uuid1()
         self.table.put(
             partition_id=self.session_id,