make default mass values consistent, invert order fmt-mass, check fmt is string

[aloctavodia]

No description provided.

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (6f270f6) 80.15% compared to head (0378a3f) 84.11%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
preliz/distributions/distributions.py	66.66%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #314      +/-   ##
==========================================
+ Coverage   80.15%   84.11%   +3.95%     
==========================================
  Files          34       35       +1     
  Lines        4178     4187       +9     
==========================================
+ Hits         3349     3522     +173     
+ Misses        829      665     -164     

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