code: public static Collection<String> getPropertiesNames(Stanza packet) {
          JivePropertiesExtension jpe = (JivePropertiesExtension) packet.getExtension(JivePropertiesExtension.NAMESPACE);
          if (jpe == null) {
              return Collections.emptyList();
          }
          return jpe.getPropertyNames();
      }
docs: Return a collection of the names of all properties of the given packet. If the packet
  contains no properties extension, then an empty collection will be returned.
  
  @param packet
  @return a collection of the names of all properties.