[CLEANUP] update prettier to v2.0.4

src/core/event_bus.ts

@@ -44,7 +44,7 @@ export class EventBus {
     }
     this.subscriptions[eventType].push({
       owner,
-      callback
+      callback,
     });
   }
 
@@ -54,7 +54,7 @@ export class EventBus {
   off(eventType: string, owner: any) {
     const subs = this.subscriptions[eventType];
     if (subs) {
-      this.subscriptions[eventType] = subs.filter(s => s.owner !== owner);
+      this.subscriptions[eventType] = subs.filter((s) => s.owner !== owner);
     }
   }
 

src/core/observer.ts

@@ -67,14 +67,14 @@ export class Observer {
           self.notifyCB();
         }
         return true;
-      }
+      },
     });
 
     const metadata = {
       value,
       proxy,
       rev: this.rev,
-      parent
+      parent,
     };
 
     this.weakMap.set(value, metadata);