Fix determination of total members

[Radonirinaunimi]

Fix the determination of the total members in the checks caused by API changes.

[scarlehoff]

Is this the only place where the vp to c++ interface is used?

[codecov]

Codecov Report

Merging #43 (ca11263) into master (fbb21c6) will not change coverage.
The diff coverage is 0.00%.

@@          Coverage Diff           @@
##           master     #43   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files          16      15    -1     
  Lines        1375    1374    -1     
======================================
+ Misses       1375    1374    -1     

Flag	Coverage Δ
unittests	0.00% <0.00%> (ø)

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Impacted Files	Coverage Δ
src/pycompressor/compressing.py	0.00% <0.00%> (ø)
src/pycompressor/__init__.py

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[Radonirinaunimi]

Is this the only place where the vp to c++ interface is used?

Yes, this is the only place.