'Set the Instance Template for this Instance Group.
:param  manager: Instance Group Manager to operate on.
:type   manager: :class:`GCEInstanceGroupManager`
:param  size: New size of Managed Instance Group.
:type   size: ``int``
:return:  True if successful
:rtype:   ``bool``'

def ex_instancegroupmanager_resize(self, manager, size):

    req_params = {'size': size}
    request = ('/zones/%s/instanceGroupManagers/%s/resize' % (manager.zone.name, manager.name))
    self.connection.async_request(request, method='POST', params=req_params)
    return True
