lemon-admin/public/vendor/fontawesome/less/_duotone-icons.less

// specific duotone icon class definition
// -------------------------

/* Font Awesome uses the Unicode Private Use Area (PUA) to ensure screen
   readers do not read off random characters that represent icons */

each(.fa-icons(), {
  .fad.@{fa-css-prefix}-@{key}::after, .@{fa-css-prefix}-duotone.@{fa-css-prefix}-@{key}::after {
    content: %("%s%s", @value, @value);
  }
});