code: @GwtIncompatible("Class.getDeclaredFields")
  	public ToStringBuilder addDeclaredFields() {
  		Field[] fields = instance.getClass().getDeclaredFields();
  		for(Field field : fields) {
  			addField(field);
  		}
  		return this;
  	}
docs: Adds all fields declared directly in the object's class to the output
  @return this