public Builder setUpdateMask(com.google.protobuf.FieldMask value) {
        if (updateMaskBuilder_ == null) {
          if (value == null) {
            throw new NullPointerException();
          }
          updateMask_ = value;
        } else {
          updateMaskBuilder_.setMessage(value);
        }
        bitField0_ |= 0x00000001;
        onChanged();
        return this;
      }
<pre>
Optional. Field mask is used to specify the fields to be overwritten in
the Draft resource by the update. The fields specified in the update_mask
are relative to the resource, not the full request. A field will be
overwritten if it is in the mask. If the user does not provide a mask
then all fields will be overwritten.
</pre>

<code>.google.protobuf.FieldMask update_mask = 1 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/UpdateApplicationInstancesRequest.java