code: final public ExpressionToken MapKey() throws ParseException {
          Token t = null;
          ExpressionToken eTok = null;
          jj_consume_token(LBRACKET);
          t = jj_consume_token(STRING_LITERAL);
          jj_consume_token(RBRACKET);
          eTok = new MapKeyToken(t.image);
          {
              if(true) return eTok;
          }
          throw new Error("Missing return statement in function");
      }
docs: handle text inside of map braces as ["..."] or ['...']