Constant UNQUOTED_CHAR 

const UNQUOTED_CHAR: (RangeInclusive<u8>, RangeInclusive<u8>, RangeInclusive<u8>, u8, u8);

unquoted-key = 1*( ALPHA / DIGIT / %x2D / %x5F ) ; A-Z / a-z / 0-9 / - / _