private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Duration,
            com.google.protobuf.Duration.Builder,
            com.google.protobuf.DurationOrBuilder>
        getTtlFieldBuilder() {
      if (ttlBuilder_ == null) {
        if (!(expirationCase_ == 14)) {
          expiration_ = com.google.protobuf.Duration.getDefaultInstance();
        }
        ttlBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Duration,
                com.google.protobuf.Duration.Builder,
                com.google.protobuf.DurationOrBuilder>(
                (com.google.protobuf.Duration) expiration_, getParentForChildren(), isClean());
        expiration_ = null;
      }
      expirationCase_ = 14;
      onChanged();
      return ttlBuilder_;
    }
<pre>
Input only. The time-to-live (TTL) or duration for the subscription. If
unspecified or set to `0`, uses the maximum possible duration.
</pre>

<code>.google.protobuf.Duration ttl = 14 [(.google.api.field_behavior) = INPUT_ONLY];</code>
java-workspaceevents/proto-google-cloud-workspaceevents-v1/src/main/java/com/google/apps/events/subscriptions/v1/Subscription.java