def ordered_ids
      @ordered_ids ||= begin
                         ActiveFedora::SolrService.query("proxy_in_ssi:#{id}",
                                                         rows: 10_000,
                                                         fl: "ordered_targets_ssim")
                                                  .flat_map { |x| x.fetch("ordered_targets_ssim", []) }
                       end
    end
def ordered_ids
      @ordered_ids ||= begin
                         ActiveFedora::SolrService.query("proxy_in_ssi:#{id}",
                                                         rows: 10_000,
                                                         fl: "ordered_targets_ssim")
                                                  .flat_map { |x| x.fetch("ordered_targets_ssim", []) }
                       end
    end
TODO: Extract this to ActiveFedora::Aggregations::ListSource