fix(tests): Resolve late binding of loop variable in assert message lambda

The `msg` parameter for `torch.testing.assert_close` within the `test_mamba_chunk_scan_cont_batch_prefill_chunking` test function used a lambda defined inside a for-loop.
This lambda captured the loop variable `i`, triggering the `B023` warning from the Ruff linter. Ruff implements this rule (originally from flake8-bugbear) to detect "late binding" issues, where a lambda captures a reference to a variable, not its value at the time of definition.
Although the current test runner likely executes the lambda immediately upon assertion failure, this pattern is a latent bug. Future changes could defer message generation, causing all failure messages to incorrectly display the final value of `i`, which would be misleading for debugging.
This commit fixes the issue by using a default argument in the lambda (`lambda x, i=i: ...`) to capture the value of `i` at definition time.
This robustly resolves the potential bug and allows for the removal of the `# noqa: B023` suppressions.

Signed-off-by: lyd1992 <liuyudong@iscas.ac.cn>
Signed-off-by: ihb2032 <1355790728@qq.com

Signed-off-by: ihb2032 <1355790728@qq.com>

Author: ihb2032

tests/kernels/mamba/test_mamba_ssm_ssd.py

@@ -539,22 +539,18 @@ def test_mamba_chunk_scan_cont_batch_prefill_chunking(chunk_size, seqlens):
             Y_ref_seq[: chunked_seqlens[i], ...],
             atol=atol,
             rtol=rtol,
-            msg=lambda x: f"seq{i} output part1 " + x,
-        )  # noqa: B023
+            msg=lambda x, i=i: f"seq{i} output part1 " + x)
         torch.testing.assert_close(
             Y_seq[chunked_seqlens[i] :, ...],
             Y_ref_seq[chunked_seqlens[i] :, ...],
             atol=atol,
             rtol=rtol,
-            msg=lambda x: f"seq{i} output part2 " + x,
-        )  # noqa: B023
+            msg=lambda x, i=i: f"seq{i} output part2 " + x)
 
         state_seq = state_chunked[i]
         state_seq_ref = state_ref[i]
-        torch.testing.assert_close(
-            state_seq,
-            state_seq_ref,
-            atol=atol,
-            rtol=rtol,
-            msg=lambda x: f"seq{i} state " + x,
-        )  # noqa: B023
+        torch.testing.assert_close(state_seq,
+                                   state_seq_ref,
+                                   atol=atol,
+                                   rtol=rtol,
+                                   msg=lambda x, i=i: f"seq{i} state " + x)