docs: public StateMachineDefinition<S, T> addState(S newState){
  		Preconditions.checkArgument(newState != null, "State name cannot be null");
  		Integer id = Integer.valueOf((int)sequencer.next());
  		Integer previousValue = states.put(newState, id);
  		if (previousValue != null){
  			throw new IllegalArgumentException("State '" + newState + "' has already been defined.");
  		}
  		return this;
  	}