configureDefaults example

if (!isset($config['handler'])) {
            $config['handler'] = HandlerStack::create();
        } elseif (!\is_callable($config['handler'])) {
            throw new InvalidArgumentException('handler must be a callable');
        }

        // Convert the base_uri to a UriInterface         if (isset($config['base_uri'])) {
            $config['base_uri'] = Psr7\Utils::uriFor($config['base_uri']);
        }

        $this->configureDefaults($config);
    }

    /** * @param string $method * @param array $args * * @return PromiseInterface|ResponseInterface * * @deprecated Client::__call will be removed in guzzlehttp/guzzle:8.0. */
    public function __call($method, $args)
    {