Can't use non-Item type with atom Collection

When using a custom, not-Item type with atom Collection, an exception occurs. For example:

@Service(Collection.class)
public class NewsComponentImpl implements Collection<String, Headline>

// Headline is regular Java Bean

Results in:

[TuscanyBindingServletWrapper]: org.apache.tuscany.sca.databinding.TransformationException: javax.xml.stream.XMLStreamException: javax.xml.bind.MarshalException

• with linked exception:
  [javax.xml.bind.JAXBException: class org.example.news.Headline nor any of its super class is known to this context.]
  at org.apache.tuscany.sca.databinding.axiom.OMElement2String.transform(OMElement2String.java:47)
  at org.apache.tuscany.sca.databinding.axiom.OMElement2String.transform(OMElement2String.java:37)