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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 connectionLostForKey(self, key):
 """ Remove lost connection from cache. @param key: key of connection that was lost @type key: L{tuple} of L{IAddress} and C{extraHash} """

        if key in self.cachedConnections:
            del self.cachedConnections[key]
        if self._shuttingDown and self._shuttingDown.get(key):
            d, self._shuttingDown[key] = self._shuttingDown[key], None
            d.callback(None)