code: func (r *rangeAllocator) filterOutServiceRange(serviceCIDR *net.IPNet) {
  	// Checks if service CIDR has a nonempty intersection with cluster
  	// CIDR. It is the case if either clusterCIDR contains serviceCIDR with
  	// clusterCIDR's Mask applied (this means that clusterCIDR contains
  	// serviceCIDR) or vice versa (which means that serviceCIDR contains
  	// clusterCIDR).
  	if !r.clusterCIDR.Contains(serviceCIDR.IP.Mask(r.clusterCIDR.Mask)) && !serviceCIDR.Contains(r.clusterCIDR.IP.Mask(serviceCIDR.Mask)) {
  		return
  	}
  
  	if err := r.cidrs.Occupy(serviceCIDR); err != nil {
  		klog.Errorf("Error filtering out service cidr %v: %v", serviceCIDR, err)
  	}
  }
docs: // Marks all CIDRs with subNetMaskSize that belongs to serviceCIDR as used,
  // so that they won't be assignable.