Use the rule notation in docstring

[rlouf]

Closes #38

[codecov]

Codecov Report

Merging #39 (685de07) into main (6feadda) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main       #39   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          295       295           
  Branches        20        20           
=========================================
  Hits           295       295           

Impacted Files	Coverage Δ
aemcmc/conjugates.py	100.00% <ø> (ø)

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