code: func Check(d *certdata.Data) *errors.Errors {
  	var e = errors.New(nil)
  
  	if d.Cert.Version != 3 {
  		e.Err("Certificate is not V3 (%d)", d.Cert.Version)
  		return e
  	}
  
  	return nil
  }
docs: // Check performs a strict verification on the extension according to the standard(s)