public Builder clearChannel() {
        channel_ = getDefaultInstance().getChannel();
        bitField0_ = (bitField0_ & ~0x00000001);
        onChanged();
        return this;
      }
<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 This builder for chaining.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/ApplicationConfigs.java