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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _find_export(self, func):
 # type: (Callable[[Tuple[Any, EndpointDescription]], bool]) -> Optional[Tuple[Any, EndpointDescription]] """ Look for an export using the given lookup method The lookup method must accept a single parameter, which is a tuple containing a service instance and endpoint description. :param func: A function to look for the excepted export :return: The found tuple or None """

        with self._exported_instances_lock:
            for val in self._exported_services.values():
                if func(val):
                    return val

            return None