How to use the sshuttle.linux.ipt_chain_exists function in sshuttle

% family_to_string(family))

        table = "mangle"

        def _ipt(*args):
            return ipt(family, table, *args)

        def _ipt_ttl(*args):
            return ipt_ttl(family, table, *args)

        mark_chain = 'sshuttle-m-%s' % port
        tproxy_chain = 'sshuttle-t-%s' % port
        divert_chain = 'sshuttle-d-%s' % port

        # basic cleanup/setup of chains
        if ipt_chain_exists(family, table, mark_chain):
            _ipt('-D', 'OUTPUT', '-j', mark_chain)
            _ipt('-F', mark_chain)
            _ipt('-X', mark_chain)

        if ipt_chain_exists(family, table, tproxy_chain):
            _ipt('-D', 'PREROUTING', '-j', tproxy_chain)
            _ipt('-F', tproxy_chain)
            _ipt('-X', tproxy_chain)

        if ipt_chain_exists(family, table, divert_chain):
            _ipt('-F', divert_chain)
            _ipt('-X', divert_chain)

table = "nat"

        def _ipt(*args):
            return ipt(family, table, *args)

        def _ipt_ttl(*args):
            return ipt_ttl(family, table, *args)

        def _ipm(*args):
            return ipt(family, "mangle", *args)

        chain = 'sshuttle-%s' % port

        # basic cleanup/setup of chains
        if ipt_chain_exists(family, table, chain):
            if user is not None:
                nonfatal(_ipm, '-D', 'OUTPUT', '-m', 'owner', '--uid-owner',
                         str(user), '-j', 'MARK', '--set-mark', str(port))
                args = '-m', 'mark', '--mark', str(port), '-j', chain
            else:
                args = '-j', chain
            nonfatal(_ipt, '-D', 'OUTPUT', *args)
            nonfatal(_ipt, '-D', 'PREROUTING', *args)
            nonfatal(_ipt, '-F', chain)
            _ipt('-X', chain)

mark_chain = 'sshuttle-m-%s' % port
        tproxy_chain = 'sshuttle-t-%s' % port
        divert_chain = 'sshuttle-d-%s' % port

        # basic cleanup/setup of chains
        if ipt_chain_exists(family, table, mark_chain):
            _ipt('-D', 'OUTPUT', '-j', mark_chain)
            _ipt('-F', mark_chain)
            _ipt('-X', mark_chain)

        if ipt_chain_exists(family, table, tproxy_chain):
            _ipt('-D', 'PREROUTING', '-j', tproxy_chain)
            _ipt('-F', tproxy_chain)
            _ipt('-X', tproxy_chain)

        if ipt_chain_exists(family, table, divert_chain):
            _ipt('-F', divert_chain)
            _ipt('-X', divert_chain)

return ipt(family, table, *args)

        def _ipt_ttl(*args):
            return ipt_ttl(family, table, *args)

        mark_chain = 'sshuttle-m-%s' % port
        tproxy_chain = 'sshuttle-t-%s' % port
        divert_chain = 'sshuttle-d-%s' % port

        # basic cleanup/setup of chains
        if ipt_chain_exists(family, table, mark_chain):
            _ipt('-D', 'OUTPUT', '-j', mark_chain)
            _ipt('-F', mark_chain)
            _ipt('-X', mark_chain)

        if ipt_chain_exists(family, table, tproxy_chain):
            _ipt('-D', 'PREROUTING', '-j', tproxy_chain)
            _ipt('-F', tproxy_chain)
            _ipt('-X', tproxy_chain)

        if ipt_chain_exists(family, table, divert_chain):
            _ipt('-F', divert_chain)
            _ipt('-X', divert_chain)