Called on reconnection. Removes all the entries which are don't
        have the remember_between_connections flag set

def _cleanup_processing_chain(self):
        """Called on reconnection. Removes all the entries which are don't
        have the remember_between_connections flag set"""
        self.log("Removing stale processing chain entries.")
        self._processing_chain = [x for x in self._processing_chain
                                  if x.remember_between_connections]