private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.memorystore.v1.Instance.ManagedBackupSource,
            com.google.cloud.memorystore.v1.Instance.ManagedBackupSource.Builder,
            com.google.cloud.memorystore.v1.Instance.ManagedBackupSourceOrBuilder>
        getManagedBackupSourceFieldBuilder() {
      if (managedBackupSourceBuilder_ == null) {
        if (!(importSourcesCase_ == 24)) {
          importSources_ =
              com.google.cloud.memorystore.v1.Instance.ManagedBackupSource.getDefaultInstance();
        }
        managedBackupSourceBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.memorystore.v1.Instance.ManagedBackupSource,
                com.google.cloud.memorystore.v1.Instance.ManagedBackupSource.Builder,
                com.google.cloud.memorystore.v1.Instance.ManagedBackupSourceOrBuilder>(
                (com.google.cloud.memorystore.v1.Instance.ManagedBackupSource) importSources_,
                getParentForChildren(),
                isClean());
        importSources_ = null;
      }
      importSourcesCase_ = 24;
      onChanged();
      return managedBackupSourceBuilder_;
    }
<pre>
Optional. Immutable. Backups that generated and managed by memorystore
service.
</pre>

<code>
.google.cloud.memorystore.v1.Instance.ManagedBackupSource managed_backup_source = 24 [(.google.api.field_behavior) = OPTIONAL, (.google.api.field_behavior) = IMMUTABLE];
</code>
java-valkey/proto-google-cloud-valkey-v1/src/main/java/com/google/cloud/memorystore/v1/Instance.java