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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def disconnect(self, token):
 """ Unregisters a callback for an event topic. @param token: Token of the callback to unregister @type token: dict """

        topic = token['topic']
        try:
            arr = self._connects[topic]
        except KeyError:
            return
        arr.remove(token['cb'])
        if len(arr) == 0:
            del self._connects[topic]