code: func limitedByDefault(usage corev1.ResourceList, limitedResources []resourcequotaapi.LimitedResource) []corev1.ResourceName {
  	result := []corev1.ResourceName{}
  	for _, limitedResource := range limitedResources {
  		for k, v := range usage {
  			// if a resource is consumed, we need to check if it matches on the limited resource list.
  			if v.Sign() == 1 {
  				// if we get a match, we add it to limited set
  				for _, matchContain := range limitedResource.MatchContains {
  					if strings.Contains(string(k), matchContain) {
  						result = append(result, k)
  						break
  					}
  				}
  			}
  		}
  	}
  	return result
  }
docs: // limitedByDefault determines from the specified usage and limitedResources the set of resources names
  // that must be present in a covering quota.  It returns empty set if it was unable to determine if
  // a resource was not limited by default.