code: public Object toInternal(Attribute<?> attribute) throws GeomajasException {
  		if (attribute instanceof PrimitiveAttribute<?>) {
  			return toPrimitiveObject((PrimitiveAttribute<?>) attribute);
  		} else if (attribute instanceof AssociationAttribute<?>) {
  			return toAssociationObject((AssociationAttribute<?>) attribute);
  		} else {
  			throw new GeomajasException(ExceptionCode.CONVERSION_PROBLEM, attribute);
  		}
  	}
docs: Converts a DTO attribute into a generic attribute object.
  
  @param attribute
  The DTO attribute.
  @return The server side attribute representation. As we don't know at this point what kind of object the
  attribute is (that's a problem for the <code>FeatureModel</code>), we return an <code>Object</code>.