code: func validatePSPRunAsUser(fldPath *field.Path, runAsUser *policy.RunAsUserStrategyOptions) field.ErrorList {
  	allErrs := field.ErrorList{}
  
  	// ensure the user strategy has a valid rule
  	supportedRunAsUserRules := sets.NewString(
  		string(policy.RunAsUserStrategyMustRunAs),
  		string(policy.RunAsUserStrategyMustRunAsNonRoot),
  		string(policy.RunAsUserStrategyRunAsAny),
  	)
  	if !supportedRunAsUserRules.Has(string(runAsUser.Rule)) {
  		allErrs = append(allErrs, field.NotSupported(fldPath.Child("rule"), runAsUser.Rule, supportedRunAsUserRules.List()))
  	}
  
  	// validate range settings
  	for idx, rng := range runAsUser.Ranges {
  		allErrs = append(allErrs, validateUserIDRange(fldPath.Child("ranges").Index(idx), rng)...)
  	}
  
  	return allErrs
  }
docs: // validatePSPRunAsUser validates the RunAsUser fields of PodSecurityPolicy.