anthropic[major]: support python 3.13 (#27916)

Last week Anthropic released version 0.39.0 of its python sdk, which
enabled support for Python 3.13. This release deleted a legacy
`client.count_tokens` method, which we currently access during init of
the `Anthropic` LLM. Anthropic has replaced this functionality with the
[client.beta.messages.count_tokens()
API](https://github.com/anthropics/anthropic-sdk-python/pull/726).

To enable support for `anthropic >= 0.39.0` and Python 3.13, here we
drop support for the legacy token counting method, and add support for
the new method via `ChatAnthropic.get_num_tokens_from_messages`.

To fully support the token counting API, we update the signature of
`get_num_tokens_from_message` to accept tools everywhere.

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>

libs/core/langchain_core/language_models/base.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import warnings
 from abc import ABC, abstractmethod
 from collections.abc import Mapping, Sequence
 from functools import cache
@@ -364,17 +365,31 @@ class BaseLanguageModel(
         """
         return len(self.get_token_ids(text))
 
-    def get_num_tokens_from_messages(self, messages: list[BaseMessage]) -> int:
+    def get_num_tokens_from_messages(
+        self,
+        messages: list[BaseMessage],
+        tools: Optional[Sequence] = None,
+    ) -> int:
         """Get the number of tokens in the messages.
 
         Useful for checking if an input fits in a model's context window.
 
+        **Note**: the base implementation of get_num_tokens_from_messages ignores
+        tool schemas.
+
         Args:
             messages: The message inputs to tokenize.
+            tools: If provided, sequence of dict, BaseModel, function, or BaseTools
+                to be converted to tool schemas.
 
         Returns:
             The sum of the number of tokens across the messages.
         """
+        if tools is not None:
+            warnings.warn(
+                "Counting tokens in tool schemas is not yet supported. Ignoring tools.",
+                stacklevel=2,
+            )
         return sum([self.get_num_tokens(get_buffer_string([m])) for m in messages])
 
     @classmethod