human
Solve the following python programming problem given the following code:
def testIncrementalRows(self) : 
    d = defer.Deferred () 
    cb = self.make_connection () 
    o = cb.queryEx (RowsHandler, 'beer', 'brewery_beers') 
    self.assertIsInstance (o, RowsHandler) 
    def verify(unused) : 
        self.assertTrue ((o.indexed_rows > 7000)) 
        self.assertEqual (o._rows_received, o.indexed_rows) 
d.addCallback (d) 
    o._d = d 
    return d 

    
    

    Fix the buggy line: d.addCallback (d)
assistant
#Here is Python code to fix the buggy line: d.

d.addCallback (def verify()