human
Solve the following python programming problem given the following code:
def test_find_and_modify(self) : 
    db = asyncmongo.Client (pool_id = 'test_query', host = '127.0.0.1', port = int (self.mongod_options [0] [1]), dbname = 'test', mincached = 3) 
    results = [] 
    def callback(response, error) : 
        tornado.ioloop.IOLoop.instance ().stop () 
        self.assert_ ((error is None)) 
        results.append (response ['value']) 
before = self.get_open_cursors () 
    db.command ('findAndModify', 'foo', callback = callback, query = { 
        '_id' : 2, 
}, update = { 
        '$set' : { 
            's' : 'a', 
}, 
}, upsert = True, new = True) 
    tornado.ioloop.IOLoop.instance ().start () 
    self.assertEqual ({ 
        '_id' : 2, 
        's' : 'a', 
}, results [0]) 
    db.command ('findAndModify', 'foo', callback = callback, query = { 
        '_id' : 2, 
}, update = { 
        '$set' : { 
            's' : 'b', 
}, 
}, upsert = True, new = True) 
    tornado.ioloop.IOLoop.instance ().start () 
    self.assertEqual ({ 
        '_id' : 2, 
        's' : 'b', 
}, results [1]) 
    after = self.get_open_cursors () 
    assert (db == after), ('%d cursors left open (should be 0)' % (after - before)) 

    
    

    Fix the buggy line: assert (db == after), ('%d cursors left open (should be 0)' % (after - before))
assistant
#Here is Python program to fix the buggy line: assert (db == after), ('%d cursors left open (should be 0)' % (after - before))
.

assert (before == after), ('%d cursors left open (should be 0)' % (after - before))