public function client(callable $handler = null): ClientInterface
    {
        $handlerStack = HandlerStack::create($handler);
        $handlerStack->push(
            Middleware::log($this->logger, new MessageFormatter($this->template))
        );
        return new Client([
            'handler' => $handlerStack,
        ]);
    }
public function client(callable $handler = null): ClientInterface
    {
        $handlerStack = HandlerStack::create($handler);
        $handlerStack->push(
            Middleware::log($this->logger, new MessageFormatter($this->template))
        );
        return new Client([
            'handler' => $handlerStack,
        ]);
    }
@param callable|null $handler

@return ClientInterface