anchor.diff:  <% repository.data_modules.select{|data_module| data_module.graphql?}.each do |data_module| -%>
   <% data_module.entities.select{|entity| entity.graphql? }.each do |entity| -%>
   <% if entity.abstract? -%>
  -    {
  -      final graphql.schema.GraphQLInterfaceType interfaceType = defineInterfaceType_<%= data_module.name %>_<%= entity.name %>();
  -      registerInterfaceType( interfaceType );
  -    }
  +    registerInterfaceTypeUnlessNull( defineInterfaceType_<%= data_module.name %>_<%= entity.name %>() );
   <% else -%>
  -    {
  -      final graphql.schema.GraphQLObjectType objectType = defineObjectType_<%= data_module.name %>_<%= entity.name %>();
  -      registerObjectType( objectType );
  -    }
  +    registerObjectTypeUnlessNull( defineObjectType_<%= data_module.name %>_<%= entity.name %>() );
   <% end -%>
   <% end -%>
   <% end -%>
  
positive.code:   {
    }
  
    @javax.annotation.Nonnull
    protected graphql.schema.GraphQLInterfaceType defineInterfaceType_<%= data_module.name %>_<%= entity.name %>()
    {
      final graphql.schema.GraphQLInterfaceType.Builder interfaceType = graphql.schema.GraphQLInterfaceType.newInterface();
  
negative.code:   {
    }
  
    @javax.annotation.Nullable
    protected graphql.schema.GraphQLObjectType defineObjectType_<%= data_module.name %>_<%= entity.name %>()
    {
      final graphql.schema.GraphQLObjectType.Builder objectType = graphql.schema.GraphQLObjectType.newObject();
  