Handle relational operators in SBML import

[dweindl]

Fixes #2651.

Related to #2146

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.16%. Comparing base (f742e48) to head (9673abd).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2652      +/-   ##
===========================================
- Coverage    77.19%   77.16%   -0.04%     
===========================================
  Files          332      332              
  Lines        23142    23142              
  Branches      1480     1480              
===========================================
- Hits         17864    17857       -7     
- Misses        5267     5274       +7     
  Partials        11       11              

Flag	Coverage Δ
cpp	74.09% <ø> (-0.04%)	⬇️
cpp_python	33.38% <ø> (ø)
petab	39.40% <ø> (ø)
python	72.21% <ø> (-0.03%)	⬇️

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Files with missing lines	Coverage Δ
python/sdist/amici/import_utils.py	89.36% <ø> (ø)

... and 2 files with indirect coverage changes