SRIOV Adapter is not getting added.

I have created VFs on vmnic5 and created a Vswitch out of it.. Created a VM IKM-testvm and trying to attach SRIOV VF to it using the following code..

vm = pyvmomi.get_obj([vim.VirtualMachine], name)
nic = vim.vm.device.VirtualDeviceSpec()

VM device

nic.operation = vim.vm.device.VirtualDeviceSpec.Operation.add
nic.device = vim.vm.device.VirtualSriovEthernetCard()
nic.device.deviceInfo = vim.Description()
nic.device.deviceInfo.label = vnic_label
nic.device.deviceInfo.summary = network_name
nic.device.backing = vim.vm.device.VirtualEthernetCard.NetworkBackingInfo()
nic.device.backing.network = pyvmomi.get_obj([vim.Network], network_name)
nic.device.backing.deviceName = network_name
nic.device.backing.useAutoDetect = False
nic.device.connectable = vim.vm.device.VirtualDevice.ConnectInfo()
nic.device.connectable.startConnected = True
nic.device.connectable.allowGuestControl = False
nic.device.connectable.connected = False

nic.device.sriovBacking = vim.vm.device.VirtualSriovEthernetCard.SriovBackingInfo()

nic.device.sriovBacking.physicalFunctionBacking = vim.vm.device.VirtualPCIPassthrough.DeviceBackingInfo()
nic.device.sriovBacking.physicalFunctionBacking.id = '0000:04:00.0'

devices.append(nic)

print nic.device
vmconf = vim.vm.ConfigSpec(deviceChange=devices)
task = vm.ReconfigVM_Task(vmconf)

But the task is not completed but gives the following exception..

vim.TaskInfo) {
dynamicType = ,
dynamicProperty = (vmodl.DynamicProperty) [],
key = 'haTask-11-vim.VirtualMachine.reconfigure-9608',
task = 'vim.Task:haTask-11-vim.VirtualMachine.reconfigure-9608',
description = ,
name = vim.VirtualMachine.Reconfigure,
descriptionId = 'VirtualMachine.reconfigure',
entity = 'vim.VirtualMachine:11',
entityName = 'IKM-testvm',
locked = (vim.ManagedEntity) [],
state = 'error',
cancelled = false,
cancelable = false,
error = (vmodl.fault.InvalidArgument) {
dynamicType = ,
dynamicProperty = (vmodl.DynamicProperty) [],
msg = 'A specified parameter was not correct: ',
faultCause = ,
faultMessage = (vmodl.LocalizableMessage) [],
invalidProperty =
},
result = ,
progress = ,
reason = (vim.TaskReasonUser) {
dynamicType = ,
dynamicProperty = (vmodl.DynamicProperty) [],
userName = 'root'
},
queueTime = 2016-04-19T11:19:32.854745Z,
startTime = 2016-04-19T11:19:32.854918Z,
completeTime = 2016-04-19T11:19:32.91381Z,
eventChainId = 9608,
changeTag = ,
parentTaskKey = ,
rootTaskKey = ,
activationId =
}

Start with the SR-IOV device configuration in the issue body and the resulting ReconfigVM_Task InvalidArgument fault. Check the vSphere API requirements for VirtualSriovEthernetCard and its SriovBackingInfo, then reproduce the reconfiguration against a VM with the stated VF and network setup. Done means the task completes successfully and the SR-IOV adapter appears on IKM-testvm.