code: func (m *InMem) IsDir(ctx context.Context, name string) bool {
  	m.Lock()
  	defer m.Unlock()
  
  	for k := range m.data {
  		if strings.HasPrefix(k, name+"/") {
  			return true
  		}
  	}
  	return false
  }
docs: // IsDir returns true if the entry is a directory