Medusa\Tree\PersistentRedBlackTree::removeMin PHP Method

    public function removeMin()
    {
        $t = $this;
        if ($t->isRoot() && !$this->isRed($t->left()) && !$this->isRed($t->right())) {
            $t = $this->flipToRed($t);
        }
        $t = $this->removeMinIn($t);
        if ($t->isRoot() && $t->isEmpty()) {
            $t = $this->flipToBlack($t);
        }
        return $t;
    }