code: public static void ensure(boolean condition, String errorMessageFormat, Object... errorMessageArgs) {
          if (!condition) {
              throw new GrammarException(errorMessageFormat, errorMessageArgs);
          }
      }
docs: Throws a GrammarException if the given condition is not met.
  
  @param condition          the condition
  @param errorMessageFormat the error message format
  @param errorMessageArgs   the error message arguments