public function insert($name, $content, $parent = null, $before = false)
    {
        if (!is_string($name)) {
            throw new \Exception('Invalid body segment key ("' . gettype($name) . '")');
        }

        if ((null !== $parent) && !is_string($parent)) {
            throw new \Exception('Invalid body segment parent key ("' . gettype($parent) . '")');
        }

        if (isset($this->_body[$name])) {
            unset($this->_body[$name]);
        }

        if ((null === $parent) || !isset($this->_body[$parent])) {
            return $this->append($name, $content);
        }

        $ins  = array($name => (string) $content);
        $keys = array_keys($this->_body);
        $loc  = array_search($parent, $keys);
        if (!$before) {
            // Increment location if not inserting before
            ++$loc;
        }

        if (0 === $loc) {
            // If location of key is 0, we're prepending
            $this->_body = $ins + $this->_body;
        } elseif ($loc >= (count($this->_body))) {
            // If location of key is maximal, we're appending
            $this->_body = $this->_body + $ins;
        } else {
            // Otherwise, insert at location specified
            $pre  = array_slice($this->_body, 0, $loc);
            $post = array_slice($this->_body, $loc);
            $this->_body = $pre + $ins + $post;
        }

        return $this;
    }