Refactor atom.dart to make code cleaner

[fzyzcjy]

Describe the changes proposed in this Pull Request.

If the PR fixes a specific issue, reference the issue with Fixes #.

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Pull Request Checklist

• If the changes are being made to code, ensure the version in pubspec.yaml is updated.
• Increment the major/minor/patch/patch-count, depending on the complexity of change
• Add the necessary unit tests to ensure the coverage does not drop
• Update the Changelog to include all changes made in this PR
• Run the set:versions command using npm or yarn. You can find this command in the package.json file in the root directory
• Include the necessary reviewers for the PR
• Update the docs if there are any API changes or additions to functionality

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[codecov]

Codecov Report

Merging #854 (9ef80aa) into master (13b7e6d) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #854      +/-   ##
==========================================
- Coverage   98.96%   98.95%   -0.01%     
==========================================
  Files          55       55              
  Lines        1924     1922       -2     
==========================================
- Hits         1904     1902       -2     
  Misses         20       20              

Flag	Coverage Δ
flutter_mobx	100.00% <ø> (ø)
mobx	98.53% <100.00%> (-0.01%)	⬇️
mobx_codegen	100.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mobx/lib/src/core/atom.dart	100.00% <100.00%> (ø)

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[pavanpodila]

Why is the code coverage dropping here? Can you please check

[fzyzcjy]

No idea... It looks equivalent indeed

[amondnet]

LGTM

[pavanpodila]

LGTM but need version change on pubspec, NPM set:versions and changelog

[ghenry]

Hi all,

This looks good to merge and close?

Thanks.

done

[amondnet]

@all-contributors please add @amondnet for review

[allcontributors]

@amondnet

I've put up a pull request to add @amondnet! 🎉