refactor(callback): simplify import statements and type annotations for better readability

src/backend/base/langflow/base/agents/callback.py

@@ -1,16 +1,16 @@
-from typing import Any, Callable, Concatenate, Dict, List
+from typing import Any, Dict, List
 from uuid import UUID
 
 from langchain.callbacks.base import AsyncCallbackHandler
 from langchain_core.agents import AgentAction, AgentFinish
 
-from langflow.schema.log import LoggableType
+from langflow.schema.log import LogFunctionType
 
 
 class AgentAsyncHandler(AsyncCallbackHandler):
     """Async callback handler that can be used to handle callbacks from langchain."""
 
-    def __init__(self, log_function: Callable[Concatenate[LoggableType | list[LoggableType], ...], None] | None = None):
+    def __init__(self, log_function: LogFunctionType | None = None):
         self.log_function = log_function
 
     async def on_tool_start(

src/backend/base/langflow/schema/log.py

@@ -1,5 +1,10 @@
-from typing import Union
+from typing import Optional, Union
 
 from pydantic import BaseModel
+from typing_extensions import Protocol
 
 LoggableType = Union[str, dict, list, int, float, bool, None, BaseModel]
+
+
+class LogFunctionType(Protocol):
+    def __call__(self, message: Union[LoggableType, list[LoggableType]], *, name: Optional[str] = None) -> None: ...