code: func (b *Builder) SelectorParam(s string) *Builder {
  	selector, err := labels.Parse(s)
  	if err != nil {
  		b.errs = append(b.errs, fmt.Errorf("the provided selector %q is not valid: %v", s, err))
  		return b
  	}
  	if selector.Empty() {
  		return b
  	}
  	if b.selectAll {
  		b.errs = append(b.errs, fmt.Errorf("found non empty selector %q with previously set 'all' parameter. ", s))
  		return b
  	}
  	return b.Selector(selector)
  }
docs: // SelectorParam defines a selector that should be applied to the object types to load.
  // This will not affect files loaded from disk or URL. If the parameter is empty it is
  // a no-op - to select all resources invoke `b.Selector(labels.Everything)`.