def export(self, exported_name, sig):
        """
        Mark a function for exporting in the extension module.
        """
        fn_args, fn_retty = sigutils.normalize_signature(sig)
        sig = typing.signature(fn_retty, *fn_args)
        if exported_name in self._exported_functions:
            raise KeyError("duplicated export symbol %s" % (exported_name))

        def decorator(func):
            entry = ExportEntry(exported_name, sig, func)
            self._exported_functions[exported_name] = entry
            return func

        return decorator

        Mark a function for exporting in the extension module.
        
numba/pycc/cc.py