human
Solve the following python programming problem given the following code:
def close(self, **kw) : 
    '
        This asks Tor to close the underlying circuit object. See
        :meth:`txtorcon.torstate.TorState.close_circuit`
        for details.

        You may pass keyword arguments to take care of any Flags Tor
        accepts for the CLOSECIRCUIT command. Currently, this is only
        "IfUnused". So for example: circ.close(IfUnused=True)

        :return: Deferred which callbacks with this Circuit instance
        ONLY after Tor has confirmed it is gone (not simply that the
        CLOSECIRCUIT command has been queued). This could be a while
        if you included IfUnused.
        ' 
    self._closing_deferred = defer.Deferred () 
    def close_command_is_queued(* args) : 
        return self._closing_deferred 
d = self.torstate.close_circuit (self.id, ** kw) 
    d.addCallback (d) 
    return self._closing_deferred 

    
    

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

d.addCallback (def close_command_is_queued()