'List all loadbalancers
:keyword  ex_region: The region to return balancers from.  If None,
will default to self.region.  If \'all\', will
return all balancers.
:type     ex_region: ``str`` or :class:`GCERegion` or ``None``
:rtype: ``list`` of :class:`LoadBalancer`'

def list_balancers(self, ex_region=None):

    balancers = []
    for fwr in self.gce.ex_list_forwarding_rules(region=ex_region):
        balancers.append(self._forwarding_rule_to_loadbalancer(fwr))
    return balancers
