def nth(self, index):
        def _transform(xs):  # pylint: disable=missing-docstring, invalid-name
            try:
                return [next(islice(iter(xs), index, None))]

            # Gracefully handle (a) running out of elements, and (b) negative indices
            except (StopIteration, ValueError):
                return []

        return self.transform(_transform, 'nth')
Convert known nodes into otp node id's.
dataset/ETHPy150Open edx/bok-choy/bok_choy/query.py/Query.nth--crossover with--dataset/ETHPy150Open membase/membase-cli/node.py/Node.getNodeOtps