@java.lang.Override
      public final boolean isInitialized() {
        byte isInitialized = memoizedIsInitialized;
        if (isInitialized == 1) return true;
        if (isInitialized == 0) return false;

        memoizedIsInitialized = 1;
        return true;
      }
<pre>
The key of the output resource, it has to be unique within the same
producer node. One producer node can output several output resources,
the key can be used to match corresponding output resources.
</pre>

<code>string key = 3;</code>

@return The bytes for key.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/Application.java