feat: helper function to constrain column type

[yuanbohan]

What's changed and what's your intention?

• helper Series function to constrain column type

Checklist

• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #67 (ec18262) into main (bec100f) will increase coverage by 0.23%.
The diff coverage is 71.72%.

@@            Coverage Diff             @@
##             main      #67      +/-   ##
==========================================
+ Coverage   79.29%   79.53%   +0.23%     
==========================================
  Files          10       11       +1     
  Lines         739      767      +28     
==========================================
+ Hits          586      610      +24     
- Misses        115      119       +4     
  Partials       38       38              

Impacted Files	Coverage Δ
metric.go	77.89% <ø> (+2.77%)	⬆️
series.go	71.72% <71.72%> (ø)

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