<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove_all_servers(self):
 """ Remove all registered WBEM servers from the subscription manager. This also unregisters listeners from these servers and removes all owned indication subscriptions, owned indication filters, and owned listener destinations. Raises: Exceptions raised by :class:`~pywbem.WBEMConnection`. """


        for server_id in list(self._servers.keys()):
            self.remove_server(server_id)