public static function get_allowed_themes() {

		static $themes;

		if ( isset( $themes ) ) {
			return $themes;
		}

		$wp_themes = wp_get_themes( array( 'allowed' => true ) );

		/** @var WP_Theme $theme */
		foreach ( $wp_themes as $theme ) {

			// Make keys names (rather than slugs) for backwards compat.
			$themes[ $theme->get( 'Name' ) ] = $theme;
		}

		$themes = apply_filters( 'tts_allowed_themes', $themes );

		return $themes;
	}