ListSubscriptions.
        Get a list of subscriptions.
        :param str publisher_id: ID for a subscription.
        :param str event_type: Maximum number of notifications to return. Default is 100.
        :param str consumer_id: ID for a consumer.
        :param str consumer_action_id: ID for a consumerActionId.
        :rtype: [Subscription]

def list_subscriptions(self, publisher_id=None, event_type=None, consumer_id=None, consumer_action_id=None):
        """ListSubscriptions.
        Get a list of subscriptions.
        :param str publisher_id: ID for a subscription.
        :param str event_type: Maximum number of notifications to return. Default is 100.
        :param str consumer_id: ID for a consumer.
        :param str consumer_action_id: ID for a consumerActionId.
        :rtype: [Subscription]
        """
        query_parameters = {}
        if publisher_id is not None:
            query_parameters['publisherId'] = self._serialize.query('publisher_id', publisher_id, 'str')
        if event_type is not None:
            query_parameters['eventType'] = self._serialize.query('event_type', event_type, 'str')
        if consumer_id is not None:
            query_parameters['consumerId'] = self._serialize.query('consumer_id', consumer_id, 'str')
        if consumer_action_id is not None:
            query_parameters['consumerActionId'] = self._serialize.query('consumer_action_id', consumer_action_id, 'str')
        response = self._send(http_method='GET',
                              location_id='fc50d02a-849f-41fb-8af1-0a5216103269',
                              version='5.0',
                              query_parameters=query_parameters)
        return self._deserialize('[Subscription]', self._unwrap_collection(response))