code: public Enumeration<String> getElements() {
          AttributeNameEnumeration elements = new AttributeNameEnumeration();
          elements.addElement(NAME + DOT + INFO);
          elements.addElement(NAME + DOT + ALG_ID);
          elements.addElement(NAME + DOT + SIGNATURE);
          elements.addElement(NAME + DOT + SIGNED_CERT);
  
          return elements.elements();
      }
docs: Return an enumeration of names of attributes existing within this
  attribute.