code: def test_prefix_sum():
      x = [3, 4, 5]
      psum = prefix_sum_inc(x)
      assert psum == [3, 7, 12]
  
imports: import pytest
  import torch
  import deepspeed.comm
  from deepspeed.runtime.utils import partition_uniform
  from deepspeed.runtime.utils import partition_balanced
  from deepspeed.runtime.utils import prefix_sum_inc
  from deepspeed.runtime.utils import PartitionedTensor
  from unit.common import DistributedTest
label_desc: Use image node_id 3 for calling a global function with example usage: test_prefix_sum() without return types