lib/MultiIniModifier.php
public function isSection($name)
    {
        return $this->overrider->isSection($name) || $this->master->isSection($name);
    }
public function isSection($name)
    {
        return $this->overrider->isSection($name) || $this->master->isSection($name);
    }
says if there is a section with the given name.