code: function $sum(params) {
      if (Array.isArray(params) && params.every(p => typeof p === 'number')) {
          return params.reduce((t, n) => t + n, 0);
      }
      throw new Error('$sum expects an array of number');
  }
docs: Sum the numbers in the array
  
  @param {number[]} params
  @returns {number}