code: function(state, transitionContext)
    {
      // this check is necessary to make sure we don't re-enter a transient state
      // like Renewing when we're already in it
      if (currentState !== state)
      {
        // if we have a current state, exit it; the null check is necessary
        // because the currentState is undefined at bootstrap time when we
        // transition to the first state
        if (currentState)
        {
          currentState.exit();
        }
  
        // update the current state
        currentState = state;
  
        // enter the new state
        currentState.enter(transitionContext);
      }
    }
docs: Transitions to a given state.
  
  @param {Object} state
  @param {Object} [transitionContext]