add method
      
void
add(
    
    
- T event
Implementation
void add(T event) {
  assert(!isClosed, 'You cannot add event to closed Stream');
  _value = event;
  _notifyData(event);
}void add(T event) {
  assert(!isClosed, 'You cannot add event to closed Stream');
  _value = event;
  _notifyData(event);
}