[CI] fix the vllm run-npu-test.sh break: cannot import _Backend from vllm.platforms

[leo-pony]

What this PR does / why we need it?

Adapt to vllm changes: "Move Backend enum into registry #25893"

Does this PR introduce any user-facing change?

No

How was this patch tested?

• vLLM version: v0.11.0rc3
• vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0

[github-actions]

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[gemini-code-assist]

Code Review

This pull request aims to fix a CI break resulting from the _Backend enum being moved in the vllm library. The current implementation uses a version check that is brittle because it relies on an exact version match. My review provides a more robust solution using a try-except block, which is a standard and more reliable way to handle such dependency changes across different versions.

[gemini-code-assist]

The use of vllm_version_is with an exact version match is brittle for ensuring compatibility across different vllm versions. This logic implies that only version 0.11.0 uses the old import path, while all other versions (both older and newer) use the new one, which is an unlikely scenario for an API migration.

A more robust and idiomatic Python pattern for handling moved imports is to use a try...except ImportError block. This approach is independent of version string formats (which can be inconsistent, especially for development builds) and directly verifies the import's availability.

Suggested change

	from vllm_ascend.utils import vllm_version_is
	if vllm_version_is("0.11.0"):
	from vllm.platforms import _Backend
	else:
	from vllm.attention.backends.registry import _Backend
	try:
	# In recent vLLM versions, _Backend was moved to the backends registry.
	from vllm.attention.backends.registry import _Backend
	except ImportError:
	# Fallback to the old location for older vLLM versions.
	from vllm.platforms import _Backend

[wangxiyuan]

we'd like to remove this patch file once ds3.2 is updated to vLLM way.