Doc example fix.

[DenisPavlov]

Itarable.forEach function returns Unit type.

[codecov]

Codecov Report

Merging #208 (6629ee0) into master (d7ea236) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #208   +/-   ##
=========================================
  Coverage     90.84%   90.84%           
  Complexity      127      127           
=========================================
  Files            44       44           
  Lines           415      415           
  Branches         55       55           
=========================================
  Hits            377      377           
  Misses           11       11           
  Partials         27       27           

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[DenisPavlov]

Hello everyone. I have made this fix and I don't understand what I should do next. Would you give me some advice?