Add `calc_new_to_total_ratio()` in __init__

[Sichao25]

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 22.84%. Comparing base (dbb833c) to head (cf3b9fa). Report is 44 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #671      +/-   ##
==========================================
- Coverage   23.14%   22.84%   -0.31%     
==========================================
  Files         162      163       +1     
  Lines       27773    28252     +479     
==========================================
+ Hits         6429     6453      +24     
- Misses      21344    21799     +455     

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