def upgrade_plan_list(self, subid, params=None):
        ''' /v1/server/upgrade_plan_list
        GET - account
        Retrieve a list of the VPSPLANIDs for which a virtual machine
        can be upgraded. An empty response array means that there are
        currently no upgrades available.

        Link: https://www.vultr.com/api/#server_upgrade_plan_list
        '''
        params = update_params(params, {'SUBID': subid})
        return self.request('/v1/server/upgrade_plan_list', params, 'GET')
/v1/server/upgrade_plan_list
        GET - account
        Retrieve a list of the VPSPLANIDs for which a virtual machine
        can be upgraded. An empty response array means that there are
        currently no upgrades available.

        Link: https://www.vultr.com/api/#server_upgrade_plan_list