code: func (f *FakeCloud) List(filter string) ([]types.NodeName, error) {
  	f.addCall("list")
  	result := []types.NodeName{}
  	for _, machine := range f.Machines {
  		if match, _ := regexp.MatchString(filter, string(machine)); match {
  			result = append(result, machine)
  		}
  	}
  	return result, f.Err
  }
docs: // List is a test-spy implementation of Instances.List.
  // It adds an entry "list" into the internal method call record.