refactor: stop returning impl in print feature

[github-actions[bot]]

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= binary-size{name="mrml-cli", platform.os="linux", platform.arch="x86_64"} 6691304.00

[codecov[bot]]

Codecov Report

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

Project coverage is 93.17%. Comparing base (5311e58) to head (22b4be4). Report is 66 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #449 +/- ## ========================================== + Coverage 92.89% 93.17% +0.28% ========================================== Files 227 202 -25 Lines 12203 12023 -180 ========================================== - Hits 11336 11203 -133 + Misses 867 820 -47 ```

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