Medusa\Tree\PersistentRedBlackTree::remove PHP Method

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