human
Solve the following python programming problem given the following code:
@ mock.patch ('nova.utils.get_image_from_system_metadata') 
def test_unshelve_volume_backed(self, mock_image_meta) : 
    instance = self._create_fake_instance_obj () 
    node = test_compute.NODENAME 
    limits = { 
        
} 
    filter_properties = { 
        'limits' : limits, 
} 
    instance.task_state = task_states.UNSHELVING 
    instance.save () 
    image_meta = { 
        'properties' : { 
            'base_image_ref' : 'fake_id', 
}, 
} 
    mock_image_meta.return_value = image_meta 
    self.mox.StubOutWithMock (self.compute, '_notify_about_instance_usage') 
    self.mox.StubOutWithMock (self.compute, '_prep_block_device') 
    self.mox.StubOutWithMock (self.compute.driver, 'spawn') 
    self.mox.StubOutWithMock (self.compute, '_get_power_state') 
    self.mox.StubOutWithMock (self.rt, 'instance_claim') 
    self.mox.StubOutWithMock (self.compute.network_api, 'setup_instance_network_on_host') 
    tracking = { 
        'last_state' : mock_image_meta.task_state, 
} 
    def check_save(expected_task_state = None) : 
        if (tracking ['last_state'] == task_states.UNSHELVING) : 
            self.assertEqual (task_states.SPAWNING, instance.task_state) 
            tracking ['last_state'] = instance.task_state 
else : 
            if (tracking ['last_state'] == task_states.SPAWNING) : 
                self.assertEqual (123, instance.power_state) 
                self.assertEqual (vm_states.ACTIVE, instance.vm_state) 
                self.assertIsNone (instance.task_state) 
                self.assertIsNone (instance.key_data) 
                self.assertFalse (instance.auto_disk_config) 
                self.assertIsNone (instance.task_state) 
                tracking ['last_state'] = instance.task_state 
else : 
                self.fail ('Unexpected save!') 
self.compute._notify_about_instance_usage (self.context, instance, 'unshelve.start') 
    self.compute._prep_block_device (self.context, instance, mox.IgnoreArg (), do_check_attach = False).AndReturn ('fake_bdm') 
   ...

    
    

    Fix the buggy line: 'last_state' : mock_image_meta.task_state ,
assistant
#Here is Python code to fix the buggy line: 'last_state' : mock_image_meta.

'last_state' : instance.task_state ,