**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

{
    ParserIdentifier id_parser;
    ParserKeyValuePairsList pairs_list_parser;
    ASTPtr identifier;
    ASTPtr expr_list_args;
    if (!id_parser.parse(pos, identifier, expected))
        return false;
    bool left_bracket_found = false;
    if (pos.get().type != TokenType::OpeningRoundBracket)
    {
        if (!brackets_can_be_omitted)
             return false;
    }
    else
    {
        ++pos;
        left_bracket_found = true;
    }
    if (!pairs_list_parser.parse(pos, expr_list_args, expected))
        return false;
    if (left_bracket_found)
    {