# File lib/mongo/operation/shared/result/aggregatable.rb, line 56
        def aggregate_write_concern_errors(count)
          return unless @replies
          @replies.each_with_index.reduce(nil) do |errors, (reply, _)|
            if write_concern_errors = reply.documents.first[Error::WRITE_CONCERN_ERRORS]
              (errors || []) << write_concern_errors.reduce(nil) do |errs, wce|
                wce.merge!('index' => count + wce['index'])
                (errs || []) << write_concern_error
              end
            end
          end
        end