code: static Token getInverseOperator(Token type) {
      switch (type) {
        case GT:
          return Token.LT;
        case LT:
          return Token.GT;
        case GE:
          return Token.LE;
        case LE:
          return Token.GE;
        default:
          throw new IllegalArgumentException("Unexpected token: " + type);
      }
    }
docs: Returns the inverse of an operator if it is invertible.
  ex. '>' ==> '<'