private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.FieldMask,
            com.google.protobuf.FieldMask.Builder,
            com.google.protobuf.FieldMaskOrBuilder>
        getUpdateMaskFieldBuilder() {
      if (updateMaskBuilder_ == null) {
        updateMaskBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.FieldMask,
                com.google.protobuf.FieldMask.Builder,
                com.google.protobuf.FieldMaskOrBuilder>(
                getUpdateMask(), getParentForChildren(), isClean());
        updateMask_ = null;
      }
      return updateMaskBuilder_;
    }
<pre>
The [FieldMask][google.protobuf.FieldMask] that specifies which fields to
update.
If update_mask isn't specified, all mutable fields are to be updated.
Valid mask path is `display_name`.
</pre>

<code>.google.protobuf.FieldMask update_mask = 2;</code>
java-vision/proto-google-cloud-vision-v1/src/main/java/com/google/cloud/vision/v1/UpdateProductSetRequest.java