'Set a backup targetpool.
:param  backup_targetpool: The existing targetpool to use for
failover traffic.
:type   backup_targetpool: :class:`GCETargetPool`
:param  failover_ratio: The percentage of healthy VMs must fall at or
below this value before traffic will be sent
to the backup targetpool (default 0.10)
:type   failover_ratio: ``float``
:return:  True if successful
:rtype:   ``bool``'

def set_backup_targetpool(self, backup_targetpool, failover_ratio=0.1):

    return self.driver.ex_targetpool_set_backup_targetpool(targetpool=self, backup_targetpool=backup_targetpool, failover_ratio=failover_ratio)
