human
Solve the following python programming problem given the following code:
def _make_requires(flag, error) : 
    '
    Builds a decorator that ensures that functions that rely on OpenSSL
    functions that are not present in this build raise NotImplementedError,
    rather than AttributeError coming out of cryptography.

    :param flag: A cryptography flag that guards the functions, e.g.
        ``Cryptography_HAS_NEXTPROTONEG``.
    :param error: The string to be used in the exception if the flag is false.
    ' 
    def _requires_decorator(func) : 
        if (not flag) : 
            @ wraps (func) 
            def explode(* args, **kwargs) : 
                raise NotImplementedError (error) 
return explode 
else : 
            return func 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def _requires_decorator(