fix the quote format same with others and docstrings

[leyao-daily]

What this PR does / why we need it:
This PR is to fix the docstrings for model_server.py and update the format with others, we need this to make it clear and readable for users.
Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Type of changes
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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Feature/Issue validation/testing:

Please describe the tests that you ran to verify your changes and relevant result summary. Provide instructions so it can be reproduced.
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• Test B

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Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Checklist:

• Have you added unit/e2e tests that prove your fix is effective or that this feature works?
• Has code been commented, particularly in hard-to-understand areas?
• Have you made corresponding changes to the documentation?

Release note:

[terrytangyuan]

/lgtm

[yuzisun]

/approve

[oss-prow-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leyao-daily, sivanantha321, terrytangyuan, yuzisun

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