extract method to update shuttle data

src/repositories/ApiBasedRepository.ts

@@ -129,7 +129,7 @@ export class ApiBasedRepository implements GetterRepository {
     }
 
     // Otherwise, call getShuttlesBySystemId to update the data
-    await this.getShuttlesBySystemId(shuttle.systemId);
+    await this.updateShuttlesForSystemIfTTL(shuttle.systemId);
 
     shuttle = this.cache.shuttleByShuttleId[shuttleId];
     if (!shuttle) return null;
@@ -144,6 +144,11 @@ export class ApiBasedRepository implements GetterRepository {
     return Promise.resolve([]);
   }
 
+  public async updateShuttlesForSystemIfTTL(systemId: string) {
+    // Update shuttleByShuttleId, shuttlesBySystemId, shuttlesByRouteId (future)
+
+  }
+
   public async getStopById(stopId: string): Promise<| null> {
     return null;
   }