public Builder clearUpdateMask() {
      bitField0_ = (bitField0_ & ~0x00000002);
      updateMask_ = null;
      if (updateMaskBuilder_ != null) {
        updateMaskBuilder_.dispose();
        updateMaskBuilder_ = null;
      }
      onChanged();
      return this;
    }
<pre>
The list of fields to be updated.
- Unset `update_mask` or set `update_mask` to be a single "*" only will
  update all updatable fields with the value provided in `collection`.
- To update `display_name` value to empty string, set it in the
`collection`
  to empty string, and set `update_mask` with "display_name". Same applies
  to other updatable string fields in the `collection`.
</pre>

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