human
Solve the following python programming problem given the following code:
def _test(self, d, send, recv, result) : 
    '
        Implementation of C{_test} which checks that the command sends C{send}
        data, and that upon reception of C{recv} the result is C{result}.

        @param d: the resulting deferred from the memcache command.
        @type d: C{Deferred}

        @param send: the expected data to be sent.
        @type send: C{str}

        @param recv: the data to simulate as reception.
        @type recv: C{str}

        @param result: the expected result.
        @type result: C{any}
        ' 
    def cb(res) : 
        self.assertEquals (res, result) 
self.assertEquals (self.transport.value (), send) 
    d.addCallback (recv) 
    self.proto.dataReceived (recv) 
    return d 

    
    

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

d.addCallback (def cb()