core[patch]: remove deprecated functions from tool binding hotpath (#29015)

(Inspired by https://github.com/langchain-ai/langchain/issues/26918)

We rely on some deprecated public functions in the hot path for tool
binding (`convert_pydantic_to_openai_function`,
`convert_python_function_to_openai_function`, and
`format_tool_to_openai_function`). My understanding is that what is
deprecated is not the functionality they implement, but use of them in
the public API -- we expect to continue to rely on them.

Here we update these functions to be private and not deprecated. We keep
the public, deprecated functions as simple wrappers that can be safely
deleted.

The `@deprecated` wrapper adds considerable latency due to its use of
the `inspect` module. This update speeds up `bind_tools` by a factor of
~100x:

Before:

![Screenshot 2025-01-03 at 11 22
55 AM](https://github.com/user-attachments/assets/94b1c433-ce12-406f-b64c-ca7103badfe0)

After:

![Screenshot 2025-01-03 at 11 23
41 AM](https://github.com/user-attachments/assets/02d0deab-82e4-45ca-8cc7-a20b91a5b5db)

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/core/langchain_core/utils/function_calling.py

@@ -75,12 +75,7 @@ def _rm_titles(kv: dict, prev_key: str = "") -> dict:
     return new_kv
 
 
-@deprecated(
+def _convert_pydantic_to_openai_function(
-    "0.1.16",
-    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
-    removal="1.0",
-)
-def convert_pydantic_to_openai_function(
     model: type,
     *,
     name: Optional[str] = None,
@@ -121,6 +116,13 @@ def convert_pydantic_to_openai_function(
     }
 
 
+convert_pydantic_to_openai_function = deprecated(
+    "0.1.16",
+    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
+    removal="1.0",
+)(_convert_pydantic_to_openai_function)
+
+
 @deprecated(
     "0.1.16",
     alternative="langchain_core.utils.function_calling.convert_to_openai_tool()",
@@ -144,7 +146,7 @@ def convert_pydantic_to_openai_tool(
     Returns:
         The tool description.
     """
-    function = convert_pydantic_to_openai_function(
+    function = _convert_pydantic_to_openai_function(
         model, name=name, description=description
     )
     return {"type": "function", "function": function}
@@ -155,12 +157,7 @@ def _get_python_function_name(function: Callable) -> str:
     return function.__name__
 
 
-@deprecated(
+def _convert_python_function_to_openai_function(
-    "0.1.16",
-    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
-    removal="1.0",
-)
-def convert_python_function_to_openai_function(
     function: Callable,
 ) -> FunctionDescription:
     """Convert a Python function to an OpenAI function-calling API compatible dict.
@@ -186,13 +183,20 @@ def convert_python_function_to_openai_function(
         error_on_invalid_docstring=False,
         include_injected=False,
     )
-    return convert_pydantic_to_openai_function(
+    return _convert_pydantic_to_openai_function(
         model,
         name=func_name,
         description=model.__doc__,
     )
 
 
+convert_python_function_to_openai_function = deprecated(
+    "0.1.16",
+    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
+    removal="1.0",
+)(_convert_python_function_to_openai_function)
+
+
 def _convert_typed_dict_to_openai_function(typed_dict: type) -> FunctionDescription:
     visited: dict = {}
     from pydantic.v1 import BaseModel
@@ -201,7 +205,7 @@ def _convert_typed_dict_to_openai_function(typed_dict: type) -> FunctionDescript
         type[BaseModel],
         _convert_any_typed_dicts_to_pydantic(typed_dict, visited=visited),
     )
-    return convert_pydantic_to_openai_function(model)  # type: ignore
+    return _convert_pydantic_to_openai_function(model)  # type: ignore
 
 
 _MAX_TYPED_DICT_RECURSION = 25
@@ -272,12 +276,7 @@ def _convert_any_typed_dicts_to_pydantic(
         return type_
 
 
-@deprecated(
+def _format_tool_to_openai_function(tool: BaseTool) -> FunctionDescription:
-    "0.1.16",
-    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
-    removal="1.0",
-)
-def format_tool_to_openai_function(tool: BaseTool) -> FunctionDescription:
     """Format tool into the OpenAI function API.
 
     Args:
@@ -290,7 +289,7 @@ def format_tool_to_openai_function(tool: BaseTool) -> FunctionDescription:
 
     is_simple_oai_tool = isinstance(tool, simple.Tool) and not tool.args_schema
     if tool.tool_call_schema and not is_simple_oai_tool:
-        return convert_pydantic_to_openai_function(
+        return _convert_pydantic_to_openai_function(
             tool.tool_call_schema, name=tool.name, description=tool.description
         )
     else:
@@ -312,6 +311,13 @@ def format_tool_to_openai_function(tool: BaseTool) -> FunctionDescription:
         }
 
 
+format_tool_to_openai_function = deprecated(
+    "0.1.16",
+    alternative="langchain_core.utils.function_calling.convert_to_openai_function()",
+    removal="1.0",
+)(_format_tool_to_openai_function)
+
+
 @deprecated(
     "0.1.16",
     alternative="langchain_core.utils.function_calling.convert_to_openai_tool()",
@@ -326,7 +332,7 @@ def format_tool_to_openai_tool(tool: BaseTool) -> ToolDescription:
     Returns:
         The tool description.
     """
-    function = format_tool_to_openai_function(tool)
+    function = _format_tool_to_openai_function(tool)
     return {"type": "function", "function": function}
 
 
@@ -408,15 +414,15 @@ def convert_to_openai_function(
         if function_copy and "properties" in function_copy:
             oai_function["parameters"] = function_copy
     elif isinstance(function, type) and is_basemodel_subclass(function):
-        oai_function = cast(dict, convert_pydantic_to_openai_function(function))
+        oai_function = cast(dict, _convert_pydantic_to_openai_function(function))
     elif is_typeddict(function):
         oai_function = cast(
             dict, _convert_typed_dict_to_openai_function(cast(type, function))
         )
     elif isinstance(function, BaseTool):
-        oai_function = cast(dict, format_tool_to_openai_function(function))
+        oai_function = cast(dict, _format_tool_to_openai_function(function))
     elif callable(function):
-        oai_function = cast(dict, convert_python_function_to_openai_function(function))
+        oai_function = cast(dict, _convert_python_function_to_openai_function(function))
     else:
         msg = (
             f"Unsupported function\n\n{function}\n\nFunctions must be passed in"