code: func (p *DefaultPolicy) UnmarshalMeta(v interface{}) error {
  	if err := json.Unmarshal(p.Meta, &v); err != nil {
  		return errors.WithStack(err)
  	}
  
  	return nil
  }
docs: // UnmarshalMeta parses the policies []byte encoded metadata and stores the result in the value pointed to by v.