public Builder setRetention(com.google.protobuf.Duration value) {
      if (retentionBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        retention_ = value;
      } else {
        retentionBuilder_.setMessage(value);
      }
      bitField0_ |= 0x00000004;
      onChanged();
      return this;
    }
<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