public static function getCities( $iso_code ) {
		$response = self::client()->get( self::api_url() .'cities', [ 'query' => [ 'iso_code' => $iso_code ] ] );

		if( $response->getStatusCode() != '200')
			return ['error' => 'Something wrong happened'];

		$response = (string)$response->getBody();
		return $response;
	}