code: public final void sendMessageTo(K target, Message m) {
  
  		outMsg.f0 = target;
  		outMsg.f1 = m;
  
  		out.collect(Either.Right(outMsg));
  	}
docs: Sends the given message to the vertex identified by the given key. If the target vertex does not exist,
  the next superstep will cause an exception due to a non-deliverable message.
  
  @param target The key (id) of the target vertex to message.
  @param m The message.