code: function getDeviceList(datastore_ctx) {
     const escaped_device_ids = [];
     for (let dk of datastore_ctx.app_public_keys) {
        escaped_device_ids.push(escape(dk.device_id));
     }
     const res = escaped_device_ids.join(',');
     return res;
  }
docs: /*
  Get query string device list from datastore context