code: func ValidateIgnorePreflightErrors(ignorePreflightErrors []string) (sets.String, error) {
  	ignoreErrors := sets.NewString()
  	allErrs := field.ErrorList{}
  
  	for _, item := range ignorePreflightErrors {
  		ignoreErrors.Insert(strings.ToLower(item)) // parameters are case insensitive
  	}
  
  	if ignoreErrors.Has("all") && ignoreErrors.Len() > 1 {
  		allErrs = append(allErrs, field.Invalid(field.NewPath("ignore-preflight-errors"), strings.Join(ignoreErrors.List(), ","), "don't specify individual checks if 'all' is used"))
  	}
  
  	return ignoreErrors, allErrs.ToAggregate()
  }
docs: // ValidateIgnorePreflightErrors validates duplicates in ignore-preflight-errors flag.