code: function makeUnique (boxes = []) {
    // boxes converted to string, for easier comparison
    const ref = [];
    const result = [];
  
    boxes.forEach((item) => {
      const item_string = item.toString();
      if (ref.indexOf(item_string) === -1) {
        ref.push(item_string);
        result.push(item);
      }
    });
  
    return result;
  }
docs: Accepts list of Boxes, returns list of unique Boxes.
  @param {Array.<Box>} [boxes=[]]
  @returns {Array.<Box>}
  @ignore