assertMethod example

    public function __construct(
        string $method,
        $uri,
        array $headers = [],
        $body = null,
        string $version = '1.1'
    ) {
        $this->assertMethod($method);
        if (!($uri instanceof UriInterface)) {
            $uri = new Uri($uri);
        }

        $this->method = strtoupper($method);
        $this->uri = $uri;
        $this->setHeaders($headers);
        $this->protocol = $version;

        if (!isset($this->headerNames['host'])) {
            $this->updateHostFromUri();
        }