code: function getFixedPositionOffsetParent(element) {
    // This check is needed to avoid errors in case one of the elements isn't defined for any reason
    if (!element || !element.parentElement || isIE()) {
      return document.documentElement;
    }
    var el = element.parentElement;
    while (el && getStyleComputedProperty(el, 'transform') === 'none') {
      el = el.parentElement;
    }
    return el || document.documentElement;
  }
docs: Finds the first parent of an element that has a transformed property defined
  @method
  @memberof Popper.Utils
  @argument {Element} element
  @returns {Element} first transformed parent or documentElement