devdocs/assets/stylesheets/pages/_async.scss

._async {
  @extend %simple;

  h3 > .type-signature {
    float: right;
    color: $textColorLight;
  }

  h3 > .signature-attributes {
    font-size: .75rem;
    font-weight: normal;
    font-style: italic;
    color: $textColorLighter;
  }
}