code: def breadcrumbs(root_depth: 0, last_page_title: nil, nav_class: 'breadcrumbs', div_class: 'scrollable')
        return if m.parent_at_depth(root_depth).nil?
        h.content_tag :nav, class: nav_class do
          h.concat h.content_tag(:div, breadcrumbs_ul(breadcrumbs_list(root_depth, last_page_title)), class: div_class)
        end
      end
docs: build page breadcrumbs from specified root_depth, default root