private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Duration,
            com.google.protobuf.Duration.Builder,
            com.google.protobuf.DurationOrBuilder>
        getRetentionFieldBuilder() {
      if (retentionBuilder_ == null) {
        retentionBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Duration,
                com.google.protobuf.Duration.Builder,
                com.google.protobuf.DurationOrBuilder>(
                getRetention(), getParentForChildren(), isClean());
        retention_ = null;
      }
      return retentionBuilder_;
    }
<pre>
Optional. How long to keep automated backups before the backups are
deleted. The value should be between 1 day and 365 days. If not specified,
the default value is 35 days.
</pre>

<code>.google.protobuf.Duration retention = 3 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-valkey/proto-google-cloud-valkey-v1/src/main/java/com/google/cloud/memorystore/v1/AutomatedBackupConfig.java