function getAttributesFromTheme(string $themeName)
{
    $theme = $this->getTheme($themeName);
    if (empty($theme)) {
        return null;
    }
    $xml = $this->getXmlFile($theme->path);
    if (empty($xml)) {
        return null;
    }
    return $this->extractAttributes($xml);
}

function caller()
{
    $attributes = getAttributesFromTheme('mytheme');
}

function getAttributesFromTheme()
{
    return Pipe::make(
        $this->getXmlFile(...),
        $this->extractAttributes(...)
    )->stopIfEmpty();
}

function caller()
{
    $attributes = getAttributesFromTheme()->run(getTheme('mytheme'));
}