Fix issue #7616 (#7617)

Fix Issue #7616 with a simpler approach to extract function names (use
`__name__` attribute)

@hwchase17

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

libs/langchain/langchain/chains/openai_functions/base.py

@@ -1,7 +1,16 @@
 """Methods for creating chains that use OpenAI function-calling APIs."""
 import inspect
-import re
-from typing import Any, Callable, Dict, List, Optional, Sequence, Tuple, Type, Union
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Type,
+    Union,
+)
 
 from pydantic import BaseModel
 
@@ -25,8 +34,7 @@ PYTHON_TO_JSON_TYPES = {
 
 def _get_python_function_name(function: Callable) -> str:
     """Get the name of a Python function."""
-    source = inspect.getsource(function)
-    return re.search(r"^def (.*)\(", source).groups()[0]  # type: ignore
+    return function.__name__
 
 
 def _parse_python_function_docstring(function: Callable) -> Tuple[str, dict]:
@@ -94,10 +102,16 @@ def _get_python_function_required_args(function: Callable) -> List[str]:
     spec = inspect.getfullargspec(function)
     required = spec.args[: -len(spec.defaults)] if spec.defaults else spec.args
     required += [k for k in spec.kwonlyargs if k not in (spec.kwonlydefaults or {})]
+
+    is_class = type(function) is type
+    if is_class and required[0] == "self":
+        required = required[1:]
     return required
 
 
-def convert_python_function_to_openai_function(function: Callable) -> Dict[str, Any]:
+def convert_python_function_to_openai_function(
+    function: Callable,
+) -> Dict[str, Any]:
     """Convert a Python function to an OpenAI function-calling API compatible dict.
 
     Assumes the Python function has type hints and a docstring with a description. If