How to WaitForUpdates from VMs in a cluster?

I am using VMWare VSphere WS SDK in Python using the suds client. I want to wait for any changes to VMs. I am specifically interested in VMs of a particular cluster. Is there a way in the propertyfilterspec to say that? I tried setting the managed object reference of the cluster in the ObjectSpec with no avail. Like:

object_spec = client_factory.create('ns0:ObjectSpec')
object_spec.obj = cluster_mor
object_spec.skip = False

Figured out myself. I had to set proper traversal spec also:

object_spec = client_factory.create('ns0:ObjectSpec')
object_spec.obj = cluster_mor
object_spec.skip = False
object_spec.selectSet = build_recursive_traversal_spec(client_factory)

def build_recursive_traversal_spec(client_factory):
    #Recurse through all ResourcePools
    rp_to_rp = client_factory.create('ns0:TraversalSpec')
    rp_to_rp.name = 'rpToRp'
    rp_to_rp.type = 'ResourcePool'
    rp_to_rp.path = 'resourcePool'
    rp_to_rp.skip = False
    rp_to_vm = client_factory.create('ns0:TraversalSpec')
    rp_to_vm.name = 'rpToVm'
    rp_to_vm.type = 'ResourcePool'
    rp_to_vm.path = 'vm'
    rp_to_vm.skip = False
    spec_array_resource_pool = [client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec')]
    spec_array_resource_pool[0].name = 'rpToRp'
    spec_array_resource_pool[1].name = 'rpToVm'
    rp_to_rp.selectSet = spec_array_resource_pool

    #Traversal through resource pool branch
    cr_to_rp = client_factory.create('ns0:TraversalSpec')
    cr_to_rp.name = 'crToRp'
    cr_to_rp.type = 'ComputeResource'
    cr_to_rp.path = 'resourcePool'
    cr_to_rp.skip = False
    spec_array_computer_resource = [client_factory.create('ns0:SelectionSpec'),
                                    client_factory.create('ns0:SelectionSpec')]
    spec_array_computer_resource[0].name = 'rpToRp'
    spec_array_computer_resource[1].name = 'rpToVm'
    cr_to_rp.selectSet = spec_array_computer_resource

    #Traversal through host branch
    cr_to_h = client_factory.create('ns0:TraversalSpec')
    cr_to_h.name = 'crToH'
    cr_to_h.type = 'ComputeResource'
    cr_to_h.path = 'host'
    cr_to_h.skip = False

    #Traversal through hostFolder branch
    dc_to_hf = client_factory.create('ns0:TraversalSpec')
    dc_to_hf.name = 'dcToHf'
    dc_to_hf.type = 'Datacenter'
    dc_to_hf.path = 'hostFolder'
    dc_to_hf.skip = False
    spec_array_datacenter_host = [client_factory.create('ns0:SelectionSpec')]
    spec_array_datacenter_host[0].name = 'visitFolders'
    dc_to_hf.selectSet = spec_array_datacenter_host

    #Traversal through vmFolder branch
    dc_to_vmf = client_factory.create('ns0:TraversalSpec')
    dc_to_vmf.name = 'dcToVmf'
    dc_to_vmf.type = 'Datacenter'
    dc_to_vmf.path = 'vmFolder'
    dc_to_vmf.skip = False
    spec_array_datacenter_vm = [client_factory.create('ns0:SelectionSpec')]
    spec_array_datacenter_vm[0].name = 'visitFolders'
    dc_to_vmf.selectSet = spec_array_datacenter_vm

    #Traversal through datastore branch
    dc_to_ds = client_factory.create('ns0:TraversalSpec')
    dc_to_ds.name = 'dcToDs'
    dc_to_ds.type = 'Datacenter'
    dc_to_ds.path = 'datastore'
    dc_to_ds.skip = False
    spec_array_datacenter_ds = [client_factory.create('ns0:SelectionSpec')]
    spec_array_datacenter_ds[0].name = 'visitFolders'
    dc_to_ds.selectSet = spec_array_datacenter_ds

    #Recurse through all hosts
    h_to_vm = client_factory.create('ns0:TraversalSpec')
    h_to_vm.name = 'hToVm'
    h_to_vm.type = 'HostSystem'
    h_to_vm.path = 'vm'
    h_to_vm.skip = False
    spec_array_host_vm = [client_factory.create('ns0:SelectionSpec')]
    spec_array_host_vm[0].name = 'visitFolders'
    h_to_vm.selectSet = spec_array_host_vm

    #Recurse through all datastores
    ds_to_vm = client_factory.create('ns0:TraversalSpec')
    ds_to_vm.name = 'dsToVm'
    ds_to_vm.type = 'Datastore'
    ds_to_vm.path = 'vm'
    ds_to_vm.skip = False
    spec_array_datastore_vm = [client_factory.create('ns0:SelectionSpec')]
    spec_array_datastore_vm[0].name = 'visitFolders'
    ds_to_vm.selectSet = spec_array_datastore_vm

    #Recurse through the folders
    visit_folders = client_factory.create('ns0:TraversalSpec')
    visit_folders.name = 'visitFolders'
    visit_folders.type = 'Folder'
    visit_folders.path = 'childEntity'
    visit_folders.skip = False
    spec_array_visit_folders = [client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec'),
                                client_factory.create('ns0:SelectionSpec')]
    spec_array_visit_folders[0].name = 'visitFolders'
    spec_array_visit_folders[1].name = 'dcToHf'
    spec_array_visit_folders[2].name = 'dcToVmf'
    spec_array_visit_folders[3].name = 'crToH'
    spec_array_visit_folders[4].name = 'crToRp'
    spec_array_visit_folders[5].name = 'dcToDs'
    spec_array_visit_folders[6].name = 'hToVm'
    spec_array_visit_folders[7].name = 'dsToVm'
    spec_array_visit_folders[8].name = 'rpToVm'
    visit_folders.selectSet = spec_array_visit_folders

    #Add all of them here
    spec_array = [visit_folders, dc_to_vmf, dc_to_ds, dc_to_hf, cr_to_h,
                  cr_to_rp, rp_to_rp, h_to_vm, ds_to_vm, rp_to_vm]
    return spec_array