def has_invalid_chars(text: str) -> bool:
return not all(ord(c) <= <NUM_LIT> for c in text)<EOL>
The ANTLR4 parser does not deal with utf characters > 4 digits.
        See: http://stackoverflow.com/questions/35938284/how-do-i-specify-a-unicode-literal-that-requires-more-than-four-hex-digits-in-an#35939479
        Also look at getCharValueFromCharInGrammarLiteral routine in tool/src/org/antlr4/v4/misc/CharSupport.java