code: function scoreBlackWhiteRun(sequence, ratios) {
          const averageSize = sum(sequence) / sum(ratios);
          let error = 0;
          ratios.forEach((ratio, i) => {
              error += Math.pow((sequence[i] - ratio * averageSize), 2);
          });
          return { averageSize, error };
      }
docs: Takes in a black white run and an array of expected ratios. Returns the average size of the run as well as the "error" - that is the amount the run diverges from the expected ratio