Stack level too deep on basic usage

[prociow]

Everything seems to be setup OK but I get a following error when trying to paste the given example into any of my files.

SystemStackError: stack level too deep
  /usr/local/lib/ruby/gems/2.4.0/gems/jekyll-3.6.0/lib/jekyll/site.rb:284:in `each'
  /usr/local/lib/ruby/gems/2.4.0/gems/jekyll-3.6.0/lib/jekyll/site.rb:284:in `find'
  /usr/local/lib/ruby/gems/2.4.0/gems/jekyll-3.6.0/lib/jekyll/site.rb:284:in `find_converter_instance'
  /Users/prociow/proxi.cloud.gitlab.io/lib/jekyll-code-tabs.rb:44:in `render'
  /Users/prociow/proxi.cloud.gitlab.io/lib/jekyll-code-tabs.rb:47:in `render'

I am not an advanced Ruby user but it seems that it goes into an uneccessary loop trying to render the code tabs.