@function __isTime($value) {
  @for $i from 1 through length($value) {
    @if (type-of($value) == "number" and index("ms" "s", unit($value)) != null) or $value == 0 {
      @return $value;
    } @else {
      @error "'#{$value}' is not a valid time value. Time values must be specified in either seconds (s) or milliseconds (ms). Please try one of the following forms: '1s', '0.2s', or '3ms'";
    }
  }
}