AdminLTE/scss/dark/bootstrap/forms/_input-group.scss

// Textual addons

.input-group-text {
  color: $input-group-addon-color-alt;
  background-color: $input-group-addon-bg-alt;
  border: $input-border-width solid $input-group-addon-border-color-alt;
}

// Rounded corners

.input-group {
  $validation-messages: "";
  @each $state in map-keys($form-validation-states-alt) {
    $validation-messages: $validation-messages + ":not(." + unquote($state) + "-tooltip)" + ":not(." + unquote($state) + "-feedback)";
  }
}  // WHAT DOES THIS DO???