// source: https://www.smashingmagazine.com/2014/06/sassy-z-index-management-for-complex-layouts/
@function tds-z-index($element) {
  $z-index: default, dropdown, tab, header, banner, side-menu, overlay, modal, toast, tooltip;
  $value: index($z-index, $element);

  @if $value {
    @return ($value - 1) * 100;
  }

  @warn 'There is no item "#{$element}" in this list; choose one of: #{$list}';
  @return null;
}