code: public URL getParent() {
          if (isField()) {
              return getCharacteristicURL();
          } else if (isCharacteristic()) {
              return getServiceURL();
          } else if (isService()) {
              return getDeviceURL();
          } else if (isDevice()) {
              return getAdapterURL();
          } else if (isAdapter()) {
              return getProtocolURL();
          } else {
              return null;
          }
      }
docs: Returns a new URL representing its "parent" component.
  @return a new URL representing its "parent" component