fix: fix documentation on fourigui

[stevenhua0320]

@sbillinge ready to review. I reviewed the online documentation on pre-release on PyPI and noticed that on api page we failed to load the source of api. This is because we didn't delete the example-package module, so it breaks at that point and fails to load the other stuffs afterwards.
This is the current online documentation of the pre-release.

And this is the local re-rendering after deleting the example-package stuff.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.78%. Comparing base (f0e31c7) to head (9da0029).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #95   +/-   ##
=======================================
  Coverage   93.78%   93.78%           
=======================================
  Files           4        4           
  Lines         177      177           
=======================================
  Hits          166      166           
  Misses         11       11           

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