'Removes one or more instances from the specified instance group,
but does not delete those instances.
Scopes needed - one of the following:
* https://www.googleapis.com/auth/cloud-platform
* https://www.googleapis.com/auth/compute
:param  instancegroup:  The Instance Group where the
specified instances will be removed.
:type   instancegroup: :class:``GCEInstanceGroup``
:param  node_list: List of nodes to add.
:type   node_list: ``list`` of :class:`Node` or ``list`` of
:class:`GCENode`
:return:  True if successful.
:rtype: ``bool``'

def ex_instancegroup_remove_instances(self, instancegroup, node_list):

    request = ('/zones/%s/instanceGroups/%s/removeInstances' % (instancegroup.zone.name, instancegroup.name))
    request_data = {'instances': [{'instance': x.extra['selfLink']} for x in node_list]}
    self.connection.async_request(request, method='POST', data=request_data)
    return True
