'Retrieves the specified data disk from a virtual machine.
service_name:
The name of the service.
deployment_name:
The name of the deployment.
role_name:
The name of the role.
lun:
The Logical Unit Number (LUN) for the disk.'

def get_data_disk(self, service_name, deployment_name, role_name, lun):

    _validate_not_none('service_name', service_name)
    _validate_not_none('deployment_name', deployment_name)
    _validate_not_none('role_name', role_name)
    _validate_not_none('lun', lun)
    return self._perform_get(self._get_data_disk_path(service_name, deployment_name, role_name, lun), DataVirtualHardDisk)
