iptables manager does not honor top param of add_rule

When I add some rules with add_rule method of IptablesTable class, sometimes the top parameter is not always honored.

to reproduce:

self.iptables.ipv4['filter'].add_chain('filter')
self.iptables.ipv4['filter'].add_rule('filter',
                                      '-s 0/0 -d 192.168.0.2 -j'
                                      ' RETURN',
                                      top=True)
self.iptables.ipv4['filter'].add_rule('filter',
                                      '-s 0/0 -d 192.168.0.3 -j'
                                      ' RETURN',
                                      top=False)
self.iptables.ipv4['filter'].add_rule('filter',
                                      '-s 0/0 -d 192.168.0.4 -j'
                                      ' RETURN',
                                      top=True)
self.iptables.apply()

the good order should be:

-s 0/0 -d 192.168.0.2 -j RETURN
-s 0/0 -d 192.168.0.4 -j RETURN
-s 0/0 -d 192.168.0.3 -j RETURN

and I get:

-s 0/0 -d 192.168.0.2 -j RETURN
-s 0/0 -d 192.168.0.3 -j RETURN
-s 0/0 -d 192.168.0.4 -j RETURN