code: func (b *Builder) FieldSelectorParam(s string) *Builder {
  	s = strings.TrimSpace(s)
  	if len(s) == 0 {
  		return b
  	}
  	if b.selectAll {
  		b.errs = append(b.errs, fmt.Errorf("found non-empty field selector %q with previously set 'all' parameter. ", s))
  		return b
  	}
  	b.fieldSelector = &s
  	return b
  }
docs: // FieldSelectorParam 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.