[CI] Try introducing isort. (#3495)

tests/kernels/test_pos_encoding.py

@@ -1,9 +1,10 @@
+from itertools import accumulate
 from typing import List, Optional
 
 import pytest
 import torch
 from allclose_default import get_default_atol, get_default_rtol
-from itertools import accumulate
+
 from vllm.model_executor.layers.rotary_embedding import get_rope
 
 IS_NEOX_STYLE = [True, False]