Source

File: wp-includes/update.php

function wp_get_translation_updates() {
	$updates    = array();
	$transients = array(
		'update_core'    => 'core',
		'update_plugins' => 'plugin',
		'update_themes'  => 'theme',
	);

	foreach ( $transients as $transient => $type ) {
		$transient = get_site_transient( $transient );

		if ( empty( $transient->translations ) ) {
			continue;
		}

		foreach ( $transient->translations as $translation ) {
			$updates[] = (object) $translation;
		}
	}

	return $updates;
}