minor improvement regarding JSON marshal

[libotony]

Description

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] New and existing E2E tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 61.62%. Comparing base (4fa7366) to head (af7d9d4). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #737 +/- ## ========================================== + Coverage 61.36% 61.62% +0.26% ========================================== Files 194 194 Lines 18223 18259 +36 ========================================== + Hits 11182 11252 +70 + Misses 5959 5908 -51 - Partials 1082 1099 +17 ```

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