/// <summary>
/// Allow proceeding state from the TransitionState
/// </summary>
/// <param name="transitionState">The state to allow to proceed the TransitionState</param>
/// <returns>A IStateMachineAllow allowing transition operations to be specified</returns>
public IStateMachineAllow <T> Allow(T transitionState)
{
return(Transitions.AddIfNotPresent(transition => transition.State, new Transition <T>(this, transitionState)));
}