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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 reject(self, reason):
 """ Reject this promise for a given reason. """

        assert self._state==self.PENDING

        self._state=self.REJECTED;
        self.reason = reason
        for errback in self._errbacks:
            try:
                errback(reason)
            except Exception:
                # Ignore errors in callbacks
                pass

        # We will never call these errbacks again, so allow
        # them to be garbage collected.  This is important since
        # they probably include closures which are binding variables
        # that might otherwise be garbage collected.
        self._errbacks = []