private function parseFromFile()
    {
        if (is_null($this->file_path)) {
            throw new StorageException('Invalid file path');
        }
        $data = unserialize(file_get_contents($this->file_path));

        if ($data === false) {
            throw new StorageException('File contents not unserializeable');
        }

        $this->tokens = $data[ 'tokens' ];
        $this->states = $data[ 'states' ];
    }