Generates a random UUID4 string.
        :param cast_to: Specify what type the UUID should be cast to. Default is `str`
        :type cast_to: callable

def uuid4(self, cast_to=str):
        """
        Generates a random UUID4 string.
        :param cast_to: Specify what type the UUID should be cast to. Default is `str`
        :type cast_to: callable
        """
        # Based on http://stackoverflow.com/q/41186818
        return cast_to(uuid.UUID(int=self.generator.random.getrandbits(128), version=4))