def close(self):
        """
        Close all open SSH connections to hosts.
        """

        for host in self._hosts_client.keys():
            try:
                self._hosts_client[host].close()
            except:
                LOG.exception("Failed shutting down SSH connection to host: %s", host)

        Close all open SSH connections to hosts.
        
st2common/st2common/runners/parallel_ssh.py