result.setMinimumNumberInstances(1);
  public Capabilities getCapabilities() {    Capabilities result = super.getCapabilities();    // attributes    result.enable(Capability.NUMERIC_ATTRIBUTES);    result.enable(Capability.DATE_ATTRIBUTES);    result.enable(Capability.MISSING_VALUES);        // class    result.enable(Capability.NUMERIC_CLASS);    result.enable(Capability.DATE_CLASS);    // other    result.setMinimumNumberInstances(1);        return result;  }