Source

File: wp-includes/class-wp-locale-switcher.php

private function load_translations( $locale ) {
		global $l10n;

		$domains = $l10n ? array_keys( $l10n ) : array();

		load_default_textdomain( $locale );

		foreach ( $domains as $domain ) {
			if ( 'default' === $domain ) {
				continue;
			}

			unload_textdomain( $domain );
			get_translations_for_domain( $domain );
		}
	}