<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def deprecated_function(func, warning=DEPRECATED_FUNCTION_WARNING):
 """Adds a `DeprecationWarning` to a function Parameters func : `callable` the function to decorate with a `DeprecationWarning` warning : `str`, optional the warning to present Notes ----- The final warning message is formatted as ``warning.format(func)`` so you can use attribute references to the function itself. See the default message as an example. """

    @wraps(func)
    def wrapped_func(*args, **kwargs):
        warnings.warn(
            DEPRECATED_FUNCTION_WARNING.format(func),
            category=DeprecationWarning,
            stacklevel=2,
        )
        return func(*args, **kwargs)

    return wrapped_func