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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 callback(self, result):
 """ Callbacks the deferreds previously produced by this object. @param result: The object which will be passed to the C{callback} method of all C{Deferred}s previously produced by this object's C{tee} method. @raise AlreadyCalledError: If L{callback} or L{errback} has already been called on this object. """

        self._setResult(result)
        self._isFailure = False

        for d in self._deferreds:
            d.callback(result)