code: func resourceVSphereDPMHostOverrideFlattenID(cluster *object.ClusterComputeResource, host *object.HostSystem) (string, error) {
  	return strings.Join([]string{cluster.Reference().Value, host.Reference().Value}, ":"), nil
  }
docs: // resourceVSphereDPMHostOverrideFlattenID makes an ID for the
  // vsphere_dpm_host_override resource.