code: func (ds *dockerService) GetNetNS(podSandboxID string) (string, error) {
  	r, err := ds.client.InspectContainer(podSandboxID)
  	if err != nil {
  		return "", err
  	}
  	return getNetworkNamespace(r)
  }
docs: // GetNetNS returns the network namespace of the given containerID. The ID
  // supplied is typically the ID of a pod sandbox. This getter doesn't try
  // to map non-sandbox IDs to their respective sandboxes.