code: func ValidateTokenRequest(tr *authentication.TokenRequest) field.ErrorList {
  	allErrs := field.ErrorList{}
  	specPath := field.NewPath("spec")
  
  	const min = 10 * time.Minute
  	if tr.Spec.ExpirationSeconds < int64(min.Seconds()) {
  		allErrs = append(allErrs, field.Invalid(specPath.Child("expirationSeconds"), tr.Spec.ExpirationSeconds, "may not specify a duration less than 10 minutes"))
  	}
  	if tr.Spec.ExpirationSeconds > 1<<32 {
  		allErrs = append(allErrs, field.Invalid(specPath.Child("expirationSeconds"), tr.Spec.ExpirationSeconds, "may not specify a duration larger than 2^32 seconds"))
  	}
  	return allErrs
  }
docs: // ValidateTokenRequest validates a TokenRequest.