docs: public static char[] getAllowedFunctionCharacters() {
          char[] chars = new char[53];
          int count = 0;
          for (int i = 65; i < 91; i++) {
              chars[count++] = (char) i;
          }
          for (int i = 97; i < 123; i++) {
              chars[count++] = (char) i;
          }
          chars[count] = '_';
          return chars;
      }