code: func (m *Matcher) Validate() error {
  	var errs []error
  	if m.NamespaceLister == nil {
  		errs = append(errs, fmt.Errorf("the namespace matcher requires a namespaceLister"))
  	}
  	if m.Client == nil {
  		errs = append(errs, fmt.Errorf("the namespace matcher requires a namespaceLister"))
  	}
  	return utilerrors.NewAggregate(errs)
  }
docs: // Validate checks if the Matcher has a NamespaceLister and Client.