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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 commit_output(cls, shard_ctx, iterator):
 """Saves output references when a shard finishes. Inside end_shard(), an output writer can optionally use this method to persist some references to the outputs from this shard (e.g a list of filenames) Args: shard_ctx: map_job_context.ShardContext for this shard. iterator: an iterator that yields json serializable references to the outputs from this shard. Contents from the iterator can be accessible later via map_job.Job.get_outputs. """

    # We accept an iterator just in case output references get too big.
    outs = tuple(iterator)
    shard_ctx._state.writer_state["outs"] = outs