[Fix] fix keypoint indices

[liqikai9]

Motivation

Modification

Fix the method to get keypoint indices.

BC-breaking (Optional)

Use cases (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Merging #1191 (62dac92) into master (ccd5d87) will not change coverage.
The diff coverage is n/a.

❗ Current head 62dac92 differs from pull request most recent head 7b55763. Consider uploading reports for the commit 7b55763 to get more accurate results

@@           Coverage Diff           @@
##           master    #1191   +/-   ##
=======================================
  Coverage   82.49%   82.49%           
=======================================
  Files         204      204           
  Lines       16144    16144           
  Branches     2886     2886           
=======================================
  Hits        13318    13318           
  Misses       2096     2096           
  Partials      730      730           

Flag	Coverage Δ
unittests	82.43% <ø> (ø)

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