Adding Fillzero

[henrydingliu]

Per #656

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.03%. Comparing base (ecf0db9) to head (67f95de).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #670      +/-   ##
==========================================
+ Coverage   85.00%   85.03%   +0.02%     
==========================================
  Files          85       85              
  Lines        4883     4890       +7     
  Branches      626      627       +1     
==========================================
+ Hits         4151     4158       +7     
  Misses        522      522              
  Partials      210      210              

Flag	Coverage Δ
unittests	85.03% <100.00%> (+0.02%)	⬆️

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