class ActionView::PartialRenderer

def render_collection
  instrument(:collection, count: @collection.size) do |payload|
    return nil if @collection.blank?
    if @options.key?(:spacer_template)
      spacer = find_template(@options[:spacer_template], @locals.keys).render(@view, @locals)
    end
    cache_collection_render(payload) do
      @template ? collection_with_template : collection_without_template
    end.join(spacer).html_safe
  end
end