get_object_version (Vapor::PersistenceManager)

    # File vapor/persistencemgr.rb, line 131
        def get_object_version( klass, oid, revision )
          raise TypeError unless oid.kind_of? Integer and revision.kind_of? Integer

          ## retrieve from backend
          attributes = @backend.get_archived_tuple( klass, oid, revision )
          if attributes.nil? then  # object with oid not found
            return nil
          end
          klass = attributes['_type']
          obj = klass.new

          load_object( obj, attributes, true )

        end