Documentation error or my error?

support
1

This example is from https://gohugo.io/templates/functions#intersect

<ul>
{{ $page_link := .Permalink }}
{{ $tags := .Params.tags }}
{{ range .Site.Pages }}
    {{ $page := . }}
    {{ $has_common_tags := intersect $tags .Params.tags | len | lt 0 }}
    {{ if and $has_common_tags (ne $page_link $page.Permalink) }}
        <li><a href="{{ $page.Permalink }}">{{ $page.Title }}</a></li>
    {{ end }}
{{ end }}
</ul>

Why has the len of the intersect be less than 0?
I would think it should be greater than 0 if there is any intersect at all.