>>> import inspect, struct
>>> help(struct.pack)
Help on built-in function pack in module _struct:

pack(...)
    pack(format, v1, v2, ...) -> bytes

    Return a bytes object containing the values v1, v2, ... packed according
    to the format string.  See help(struct) for more on format strings.

>>> inspect.signature(struct.pack)
Traceback (most recent call last):
  File "<python-input-6>", line 1, in <module>
    inspect.signature(struct.pack)
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/local/lib/python3.15/inspect.py", line 3346, in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped,
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                   globals=globals, locals=locals, eval_str=eval_str,
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                   annotation_format=annotation_format)
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.15/inspect.py", line 3061, in from_callable
    return _signature_from_callable(obj, sigcls=cls,
                                    follow_wrapper_chains=follow_wrapped,
                                    globals=globals, locals=locals, eval_str=eval_str,
                                    annotation_format=annotation_format)
  File "/usr/local/lib/python3.15/inspect.py", line 2542, in _signature_from_callable
    return _signature_from_builtin(sigcls, obj,
                                   skip_bound_arg=skip_bound_arg)
  File "/usr/local/lib/python3.15/inspect.py", line 2326, in _signature_from_builtin
    raise ValueError("no signature found for builtin {!r}".format(func))
ValueError: no signature found for builtin <built-in function pack>