from typing import Callable


def make_unknown_function(func_name: str) -> Callable:
    """
    Returns a stub function in place of a function that could not be reimported.
    """

    def unknown_function(*args, **kwargs):
        raise ValueError(f"Function '{func_name}' cannot be found.")

    # Mark this function as an unknown function.
    unknown_function.unknown_function = True  # type: ignore
    return unknown_function