docs: 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)