docs: public static double sumOfProducts(double[]... nums) {
          if (nums == null || nums.length < 1)
              return 0;
          double sum = 0;
  
          for (int i = 0; i < nums.length; i++) {
              /* The ith column for all of the rows */
              double[] column = column(i, nums);
              sum += times(column);
  
          }
          return sum;
      }