How to use the messagebird.call_flow.CallFlowNumberList function in messagebird

def call_flow_numbers_add(self, call_flow_id, numbers=()):
        params = {'numbers': numbers}
        return CallFlowNumberList().load(
            self.request('call-flows/' + str(call_flow_id) + '/numbers', 'POST', params, VOICE_TYPE))

def __init__(self):
        self._data = None
        self._pagination = None

        super(CallFlowNumberList, self).__init__(CallFlowNumber)

def call_flow_numbers_list(self, call_flow_id):
        return CallFlowNumberList().load(
            self.request('call-flows/' + str(call_flow_id) + '/numbers', 'GET', None, VOICE_TYPE))