code: func DeleteExtension(tx Tx, id string) error {
  	e := tx.get(tableExtension, id)
  	if e == nil {
  		return ErrNotExist
  	}
  
  	resources, err := FindResources(tx, ByKind(e.(extensionEntry).Annotations.Name))
  	if err != nil {
  		return err
  	}
  
  	if len(resources) != 0 {
  		return errors.New("cannot delete extension because objects of this type exist in the data store")
  	}
  
  	return tx.delete(tableExtension, id)
  }
docs: // DeleteExtension removes an extension from the store.
  // Returns ErrNotExist if the object doesn't exist.