Zend\Diactoros\MessageTrait::getStream PHP Method

    private function getStream($stream, $modeIfNotInstance)
    {
        if ($stream instanceof StreamInterface) {
            return $stream;
        }
        if (!is_string($stream) && !is_resource($stream)) {
            throw new InvalidArgumentException('Stream must be a string stream resource identifier, ' . 'an actual stream resource, ' . 'or a Psr\\Http\\Message\\StreamInterface implementation');
        }
        return new Stream($stream, $modeIfNotInstance);
    }