A parallel version of the Dataset.interleave() transformation. (deprecated)

parallel_interleave() maps map_func across its input to produce nested datasets, and outputs their elements interleaved. Unlike, it gets elements from cycle_length nested datasets in parallel, which increases the throughput, especially in the presence of stragglers. Furthermore, the sloppy argument can be used to improve performance, by relaxing the requirement that the outputs are produced in a deterministic order, and allowing the implementation to skip over nested datasets whose elements are not readily available when requested.

Example usage: