human
Solve the following python programming problem given the following code:
def test_constructor_missing_cluster(self) : 
    from gcloud._testing import _Monkey 
    from gcloud.bigtable.happybase import connection as MUT 
    cluster = _Cluster () 
    timeout = object () 
    get_cluster_called = [] 
    def mock_get_cluster(timeout) : 
        get_cluster_called.append (timeout) 
        return cluster 
with _Monkey (MUT, _get_cluster = <MASK>) : 
        connection = self._makeOne (autoconnect = False, cluster = None, timeout = timeout) 
        self.assertEqual (connection.table_prefix, None) 
        self.assertEqual (connection.table_prefix_separator, '_') 
        self.assertEqual (connection._cluster, cluster) 
self.assertEqual (get_cluster_called, [timeout]) 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: self, timeout, cluster, connection, get_cluster_called
assistant
#Here is a proper replacement for <MASK>.
def mock_get_cluster(