# File lib/ai4r/data/data_set.rb, line 244
      def check_data_labels(labels)
        if !@data_items.empty?
          if labels.length != @data_items.first.length
            raise ArgumentError,
                  "Number of labels and attributes do not match. " +
                          "#{labels.length} labels and " +
                          "#{@data_items.first.length} attributes found."
          end
        end
      end