code: func (t *ProgressEmitter) Deregister(s *sharedPullerState) {
  	t.mut.Lock()
  	defer t.mut.Unlock()
  
  	if t.disabled {
  		l.Debugln("progress emitter: disabled, skip deregistering")
  		return
  	}
  
  	l.Debugln("progress emitter: deregistering", s.folder, s.file.Name)
  	delete(t.registry[s.folder], s.file.Name)
  }
docs: // Deregister a puller which will stop broadcasting pullers state.