code: def test_combine(ray_start_regular_shared):
      it = from_range(4, 1).combine(lambda x: [x, x])
      assert (
          repr(it)
          == "ParallelIterator[from_range[4, shards=1].combine()]"
      )
      assert list(it.gather_sync()) == [0, 0, 1, 1, 2, 2, 3, 3]
  
imports: import sys
  import time
  import collections
  from collections import Counter
  import pytest
  import ray
  from ray.util.iter import from_items, from_iterators, from_range, from_actors, ParallelIteratorWorker, LocalIterator
  from ray._private.test_utils import Semaphore
label_desc: Use image node_id 15 for calling a global function with example usage: test_combine(ray_start_regular_shared) without return types