code: function clockwise(placement, counter = false) {
    const index = validPlacements.indexOf(placement);
    const arr = validPlacements.slice(index + 1).concat(validPlacements.slice(0, index));
    return counter ? arr.reverse() : arr;
  }
docs: Given an initial placement, returns all the subsequent placements
  clockwise (or counter-clockwise).
  
  @method
  @memberof Popper.Utils
  @argument {String} placement - A valid placement (it accepts variations)
  @argument {Boolean} counter - Set to true to walk the placements counterclockwise
  @returns {Array} placements including their variations