You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: null.go
    path of file: ./repos/moby/libnetwork/ipams/null
    
    the code of the file until where you have to start completion: // Package null implements the null ipam driver. Null ipam driver satisfies ipamapi contract,
// but does not effectively reserve/allocate any address pool or address
package null

import (
	"net"

	"github.com/docker/docker/libnetwork/ipamapi"
	"github.com/docker/docker/libnetwork/types"
)

const (
	
    
func (a *allocator) RequestPool(addressSpace, requestedPool, requestedSubPool string, _ map[string]string, v6 bool) (string, *net.IPNet, map[string]string, error) {
	if addressSpace != defaultAddressSpace {
		return "", nil, nil, types.InvalidParameterErrorf("unknown address space: %s", addressSpace)
	}
	if requestedPool != "" {
		return "", nil, nil, types.InvalidParameterErrorf("null ipam driver does not handle specific address pool requests")
	}
	if requestedSubPool != "" {
		return "", nil, nil, types.InvalidParameterErrorf("null ipam driver does not handle specific address subpool requests")
	}
	if v6 {
		return "", nil, nil, types.InvalidParameterErrorf("null ipam driver does not handle IPv6 address pool requests")
	}
	return defaultPoolID, defaultPool, nil, nil
}