code: public EventId registerEvent(V value, long timestamp) throws Exception {
  		return sharedBuffer.registerEvent(value, timestamp);
  	}
docs: Adds another unique event to the shared buffer and assigns a unique id for it. It automatically creates a
  lock on this event, so it won't be removed during processing of that event. Therefore the lock should be removed
  after processing all {@link org.apache.flink.cep.nfa.ComputationState}s
  
  <p><b>NOTE:</b>Should be called only once for each unique event!
  
  @param value event to be registered
  @return unique id of that event that should be used when putting entries to the buffer.
  @throws Exception Thrown if the system cannot access the state.