protected function multiPolygon()
    {
        $this->match(Lexer::T_OPEN_PARENTHESIS);

        $polygons = array($this->polygon());

        $this->match(Lexer::T_CLOSE_PARENTHESIS);

        while ($this->lexer->isNextToken(Lexer::T_COMMA)) {
            $this->match(Lexer::T_COMMA);
            $this->match(Lexer::T_OPEN_PARENTHESIS);

            $polygons[] = $this->polygon();

            $this->match(Lexer::T_CLOSE_PARENTHESIS);
        }

        return $polygons;
    }