function bootstrap_form_system_theme_settings_alter

8.x-3.x bootstrap.theme bootstrap_form_system_theme_settings_alter(&$data, &$context1 = NULL, &$context2 = NULL)
7.x-3.x theme-settings.php bootstrap_form_system_theme_settings_alter(&$form, $form_state, $form_id = NULL)

Source ./bootstrap.theme (line 83)

function bootstrap_form_system_theme_settings_alter(&$data, &$context1 = NULL, &$context2 = NULL) {
  Bootstrap::alter(__FUNCTION__, $data, $context1, $context2);
}