public function getHeadersString(\Psr\Http\Message\ResponseInterface $psr7response)
    {
        $strHeaders = '';
        if($psr7response === null)
        {
            return $strHeaders;
        }

        $arrHeaders = $psr7response->getHeaders();
        if (!is_array($arrHeaders) || count($arrHeaders) < 1) {
            return '';
        }

        foreach ($arrHeaders as $key => $value) {

            $strVal = '';
            if(is_array($value) && count($value)>0){
                $strVal = $value[0];

            }elseif (is_string($value)){
                $strVal = $value;
            }

            $strHeaders .= $key.':'.$strVal.PHP_EOL;
        }

        return $strHeaders;
    }