code: public boolean isKnownMarshallable(Class<?> type) {
        MarshallingType marshallingType = typeHints.get(type);
        return marshallingType != null && marshallingType.isMarshallable != null;
     }
docs: Returns whether the hint on whether a particular type is marshallable or
  not is available. This method can be used to avoid attempting to marshall
  a type, if the hints for the type have already been calculated.
  
  @param type Marshallable type to check whether an attempt to mark it as
  marshallable has been made.
  @return true if the type has been marked as marshallable at all, false
  if no attempt has been made to mark the type as marshallable.