Fix the bug that fallback does not support more than one output

[cyfwry]

Signed-off-by: liangtao07 liangtao07@meituan.com

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #811

Type of change

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• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes

[narendasan]

cc @inocsin

[peri044]

LGTM

[cyfwry]

I have ran run_cpp_linter.py locally and modify the code format.