code: func (a *allocator) RequestAddress(poolID string, prefAddress net.IP, opts map[string]string) (*net.IPNet, map[string]string, error) {
  	logrus.Debugf("RequestAddress(%s, %v, %v)", poolID, prefAddress, opts)
  	_, ipNet, err := net.ParseCIDR(poolID)
  
  	if err != nil {
  		return nil, nil, err
  	}
  
  	if prefAddress != nil {
  		return &net.IPNet{IP: prefAddress, Mask: ipNet.Mask}, nil, nil
  	}
  
  	return nil, nil, nil
  }
docs: // RequestAddress returns an address from the specified pool ID.
  // Always allocate the 0.0.0.0/32 ip if no preferred address was specified