add doctests for example 1/n

[Borda]

What does this PR do?

We shall at least to instantiate all models in examples with default/minimal parameters

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[codecov]

Codecov Report

Merging #5079 (6c00b9e) into master (a94f662) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5079   +/-   ##
======================================
- Coverage      93%     93%   -0%     
======================================
  Files         134     134           
  Lines        9928    9928           
======================================
- Hits         9242    9235    -7     
- Misses        686     693    +7     

[justusschock]

One minor comm. Else lgtm