hugo-book-theme/layouts/shortcodes/tabs.html

{{ if .Inner }}{{ end }}
{{ $id := .Get 0 }}
{{ $group := printf "tabs-%s" $id }}

<div class="book-tabs">
{{- range $index, $tab :=  .Scratch.Get $group -}}
  <input type="radio" class="hidden" name="{{ $group }}" id="{{ printf "%s-%d" $group $index }}" {{ if not $index }}checked="checked"{{ end }} />
  <label for="{{ printf "%s-%d" $group $index }}">
    {{ $tab.Name }}
  </label>
  <div class="book-tabs-content markdown-inner">
    {{ .Content | markdownify }}
  </div>
{{- end -}}
</div>