code: func (a *allocator) ReleaseAddress(poolID string, address net.IP) error {
  	var relAddress string
  	if address != nil {
  		relAddress = address.String()
  	}
  	req := &api.ReleaseAddressRequest{PoolID: poolID, Address: relAddress}
  	res := &api.ReleaseAddressResponse{}
  	return a.call("ReleaseAddress", req, res)
  }
docs: // ReleaseAddress releases the address from the specified address pool