Flow\Parser::parseInclusionExpression PHP Method

    protected function parseInclusionExpression()
    {
        static $operators = array('not', 'in');
        $line = $this->stream->getCurrentToken()->getLine();
        $left = $this->parseCompareExpression();
        while ($this->stream->test(Token::OPERATOR, $operators)) {
            if ($this->stream->consume(Token::OPERATOR, 'not')) {
                $this->stream->expect(Token::OPERATOR, 'in');
                $right = $this->parseCompareExpression();
                $left = new Expression\NotExpression(new Expression\InclusionExpression($left, $right, $line), $line);
            } else {
                $this->stream->expect(Token::OPERATOR, 'in');
                $right = $this->parseCompareExpression();
                $left = new Expression\InclusionExpression($left, $right, $line);
            }
        }
        return $left;
    }