human
Solve the following python programming problem given the following code:
def fake_get_instance_nw_info(test, num_networks = 1, ips_per_vif = 2, floating_ips_per_fixed_ip = 0) : 
    network = network_manager.FlatManager (host = HOST) 
    network.db = db 
    global floating_ip_id, fixed_ip_id, fixed_ips 
    floating_ip_id = floating_ip_ids () 
    fixed_ip_id = fixed_ip_ids () 
    fixed_ips = [] 
    def fixed_ips_fake(* args, **kwargs) : 
        global fixed_ips 
        ips = [next_fixed_ip (i, floating_ips_per_fixed_ip) for i in range (1, (num_networks + 1)) for j in range (ips_per_vif)] 
        fixed_ips = ips 
        return ips 
def update_cache_fake(* args, **kwargs) : 
        fake_info_cache = { 
            'created_at' : None, 
            'updated_at' : None, 
            'deleted_at' : None, 
            'deleted' : False, 
            'instance_uuid' : uuids.vifs_1, 
            'network_info' : '[]', 
} 
        return fake_info_cache 
test.stub_out ('nova.db.fixed_ip_get_by_instance', fixed_ips_fake) 
    test.stub_out ('nova.db.instance_info_cache_update', <MASK>) 
    class FakeContext (nova.context.RequestContext) : 
        def is_admin(self) : 
            return True 
nw_model = network.get_instance_nw_info (FakeContext ('fakeuser', 'fake_project'), 0, 3, None) 
    return nw_model 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: floating_ips_per_fixed_ip, fixed_ips_fake, fixed_ip_id, floating_ip_id, ips_per_vif, num_networks, nw_model, test, network, fixed_ips
assistant
#Here is a proper replacement for <MASK>.
def update_cache_fake(