code: public void notifyKvStateUnregistered(
  			JobVertexID jobVertexId,
  			KeyGroupRange keyGroupRange,
  			String registrationName) {
  
  		KvStateLocation location = lookupTable.get(registrationName);
  
  		if (location != null) {
  			// Duplicate name if vertex IDs don't match
  			if (!location.getJobVertexId().equals(jobVertexId)) {
  				throw new IllegalArgumentException("Another operator (" +
  						location.getJobVertexId() + ") registered the KvState " +
  						"under '" + registrationName + "'.");
  			}
  
  			location.unregisterKvState(keyGroupRange);
  
  			if (location.getNumRegisteredKeyGroups() == 0) {
  				lookupTable.remove(registrationName);
  			}
  		} else {
  			throw new IllegalArgumentException("Unknown registration name '" +
  					registrationName + "'. " + "Probably registration/unregistration race.");
  		}
  	}
docs: Notifies the registry about an unregistered KvState instance.
  
  @param jobVertexId JobVertexID the KvState instance belongs to
  @param keyGroupRange Key group index the KvState instance belongs to
  @param registrationName Name under which the KvState has been registered
  @throws IllegalArgumentException If another operator registered the state instance
  @throws IllegalArgumentException If the registration name is not known