'Attaches load balancer to one or more subnets.
Attaching subnets that are already registered with the
Load Balancer has no effect.
:type subnets: string or List of strings
:param subnets: The name of the subnet(s) to add.'

def attach_subnets(self, subnets):

    if isinstance(subnets, six.string_types):
        subnets = [subnets]
    new_subnets = self.connection.attach_lb_to_subnets(self.name, subnets)
    self.subnets = new_subnets
