code: public void unregisterPartition(ResultPartitionID partitionId) {
  		checkNotNull(partitionId);
  
  		synchronized (registeredHandlers) {
  			LOG.debug("unregistering {}", partitionId);
  			// NOTE: tolerate un-registration of non-registered task (unregister is always called
  			//       in the cleanup phase of a task even if it never came to the registration - see
  			//       Task.java)
  			registeredHandlers.remove(partitionId);
  		}
  	}
docs: Removes the given partition from listening to incoming task events, thus forbidding calls to
  {@link #subscribeToEvent(ResultPartitionID, EventListener, Class)}.
  
  @param partitionId
  the partition ID