docs: function handleInvalidStateChanges(newState) {
          if (!isValidState(newState)) {
            signalChangeFailed('\'' + newState + '\' is not a valid state', newState);
  
            return false;
          }
  
          if (!isValidTransition(currentState, newState)) {
            signalChangeFailed('\'' + currentState + '\' cannot transition to \'' +
              newState + '\'', newState);
  
            return false;
          }
  
          return true;
        }