@java.lang.Override
    public java.lang.String getChannel() {
      java.lang.Object ref = channel_;
      if (ref instanceof java.lang.String) {
        return (java.lang.String) ref;
      } else {
        com.google.protobuf.ByteString bs = (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        channel_ = s;
        return s;
      }
    }
<pre>
The delivery channel for the event notification, only pub/sub topic is
supported now.
Example channel:
[//pubsub.googleapis.com/projects/visionai-testing-stable/topics/test-topic]
</pre>

<code>string channel = 1;</code>

@return The channel.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/ApplicationConfigs.java