[Port] New s_metric method

[etiennedeg]

This is a port of #1548

[codecov[bot]]

Codecov Report

Merging #28 (007de78) into master (6ab2160) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #28   +/-   ##
=======================================
  Coverage   99.45%   99.46%           
=======================================
  Files         106      107    +1     
  Lines        5554     5562    +8     
=======================================
+ Hits         5524     5532    +8     
  Misses         30       30           

[simonschoelly]

@etiennedeg @vboussange This PR already looks quite good, but I think we need to fix a few things before we can merge it.