private function _isFunction()
{
$peek = $this->_lexer->peek();
$nextpeek = $this->_lexer->peek();
$this->_lexer->resetPeek();
// We deny the COUNT(SELECT * FROM User u) here. COUNT won't be considered a function
return ($peek['value'] === '(' && $nextpeek['type'] !== Lexer::T_SELECT);
}