@function _is-greater-than-three-level-map($map) {
  @each $v in _filter-function(map-values($map), _is-a-map) {
    @each $v2 in _filter-function(map-values($v), _is-a-map) {
      @if type-of($v2) == map { @return true; }
    }
  }
  @return false;
}

@function _expand-implicit-selector($map) {
  @if _is-greater-than-three-level-map($map) {
    @return $map;
  } @else {
    @return ('&': $map);
  }
}