public function set($name, $value, $offset = 0)
    {
        $s = $this->getNormalizedHeaderName($name);
        if (!isset($this->headerMap[$s][$offset])) {
            $this->add($name, $value);
            return;
        }
        $i = $this->headerMap[$s][$offset];
        $this->headers[$i] = [ $name, $value ];
        $this->headerObjects[$i] = null;
    }