@function _is-not-kf-property($v) {
  @return not (
    type-of($v) == string and
    str-slice($v, 1, 4) == _kf-
  );

}

@function _kf-properties-extractor($map) {
  @return _partition-map-by-key(
    $map,
    _is-not-kf-property
  );
}