code: func lexInsideBraces(l *lexer) stateFn {
  	if strings.HasPrefix(l.input[l.pos:], lineComment) {
  		return lexLineComment
  	}
  
  	switch r := l.next(); {
  	case r == eof:
  		return l.errorf("unexpected end of input inside braces")
  	case isSpace(r):
  		return lexSpace
  	case isAlpha(r):
  		l.backup()
  		return lexIdentifier
  	case r == ',':
  		l.emit(ItemComma)
  	case r == '"' || r == '\'':
  		l.stringOpen = r
  		return lexString
  	case r == '`':
  		l.stringOpen = r
  		return lexRawString
  	case r == '=':
  		if l.next() == '~' {
  			l.emit(ItemEQLRegex)
  			break
  		}
  		l.backup()
  		l.emit(ItemEQL)
  	case r == '!':
  		switch nr := l.next(); {
  		case nr == '~':
  			l.emit(ItemNEQRegex)
  		case nr == '=':
  			l.emit(ItemNEQ)
  		default:
  			return l.errorf("unexpected character after '!' inside braces: %q", nr)
  		}
  	case r == '{':
  		return l.errorf("unexpected left brace %q", r)
  	case r == '}':
  		l.emit(ItemRightBrace)
  		l.braceOpen = false
  
  		if l.seriesDesc {
  			return lexValueSequence
  		}
  		return lexStatements
  	default:
  		return l.errorf("unexpected character inside braces: %q", r)
  	}
  	return lexInsideBraces
  }
docs: // lexInsideBraces scans the inside of a vector selector. Keywords are ignored and
  // scanned as identifiers.