code: function checkApplication(jdlApplication) {
    if (!jdlApplication || !jdlApplication.config) {
      throw new Error('An application must be passed to be validated.');
    }
    applicationConfig = jdlApplication.config;
    checkForValidValues();
    checkForNoDatabaseType();
    checkForInvalidDatabaseCombinations();
  }
docs: Checks whether a JDL application is valid. If everything's okay, no exception is thrown.
  @param jdlApplication the application to check