code: public StateConfiguration<S, T> permitInternal(T trigger, Action action) {
          return permitInternalIf(trigger, NO_GUARD, action);
      }
docs: Accept the specified trigger, execute action and stay in state
  <p>
  Applies to the current state only. No exit or entry actions will be
  executed and the state will not change. The only thing that happens is
  the execution of a given action.
  
  @param trigger The accepted trigger
  @param action  The action to be performed
  @return The receiver