[nnx] Fix nnx basics

[cgarciae]

What does this PR do?

Fixes nnx_basics guide to use static as the first return argument of split.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.87%. Comparing base (5d9fd9f) to head (fbfc0d0).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3812      +/-   ##
==========================================
+ Coverage   60.86%   60.87%   +0.01%     
==========================================
  Files         105      105              
  Lines       13045    13052       +7     
==========================================
+ Hits         7940     7946       +6     
- Misses       5105     5106       +1     

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