langchain[patch]: Asynchronous human-in-the-loop callback (#14195)

**Description:** Adding a possibility to use asynchronous callback
handler in human-in-the-loop validation tool. Very useful, for example,
if you want to implement a validation over Telegram bot.
**Issue:** -
**Dependencies:** -

---------

Co-authored-by: Daniyar_Supiyev <daniyar_supiyev@epam.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/langchain/langchain/callbacks/human.py

@@ -1,7 +1,7 @@
-from typing import Any, Callable, Dict, Optional
+from typing import Any, Awaitable, Callable, Dict, Optional
 from uuid import UUID
 
-from langchain.callbacks.base import BaseCallbackHandler
+from langchain.callbacks.base import AsyncCallbackHandler, BaseCallbackHandler
 
 
 def _default_approve(_input: str) -> bool:
@@ -14,6 +14,16 @@ def _default_approve(_input: str) -> bool:
     return resp.lower() in ("yes", "y")
 
 
+async def _adefault_approve(_input: str) -> bool:
+    msg = (
+        "Do you approve of the following input? "
+        "Anything except 'Y'/'Yes' (case-insensitive) will be treated as a no."
+    )
+    msg += "\n\n" + _input + "\n"
+    resp = input(msg)
+    return resp.lower() in ("yes", "y")
+
+
 def _default_true(_: Dict[str, Any]) -> bool:
     return True
 
@@ -48,3 +58,31 @@ class HumanApprovalCallbackHandler(BaseCallbackHandler):
             raise HumanRejectedException(
                 f"Inputs {input_str} to tool {serialized} were rejected."
             )
+
+
+class AsyncHumanApprovalCallbackHandler(AsyncCallbackHandler):
+    """Asynchronous callback for manually validating values."""
+
+    raise_error: bool = True
+
+    def __init__(
+        self,
+        approve: Callable[[Any], Awaitable[bool]] = _adefault_approve,
+        should_check: Callable[[Dict[str, Any]], bool] = _default_true,
+    ):
+        self._approve = approve
+        self._should_check = should_check
+
+    async def on_tool_start(
+        self,
+        serialized: Dict[str, Any],
+        input_str: str,
+        *,
+        run_id: UUID,
+        parent_run_id: Optional[UUID] = None,
+        **kwargs: Any,
+    ) -> Any:
+        if self._should_check(serialized) and not await self._approve(input_str):
+            raise HumanRejectedException(
+                f"Inputs {input_str} to tool {serialized} were rejected."
+            )