private XSDTypeDefinition getXSDTypeDefinition(XSDAttributeDeclaration attribute) {
   // port to org.eclipse.xsd
   if (attribute.getTypeDefinition() != null) return attribute.getTypeDefinition();
   // port to org.eclipse.xsd
   else if (attribute.getAnonymousTypeDefinition() != null)
     return attribute.getAnonymousTypeDefinition();
   else return null;
 }