visit_hash_subclass

# File ext/psych/lib/psych/visitors/yaml_tree.rb, line 454
      def visit_hash_subclass o
        ivars = o.instance_variables
        if ivars.any?
          tag = "!ruby/hash-with-ivars:#{o.class}"
          node = @emitter.start_mapping(nil, tag, false, Psych::Nodes::Mapping::BLOCK)
          register(o, node)

          # Dump the elements
          accept 'elements'
          @emitter.start_mapping nil, nil, true, Nodes::Mapping::BLOCK
          o.each do |k,v|
            accept k
            accept v
          end
          @emitter.end_mapping

          # Dump the ivars
          accept 'ivars'
          @emitter.start_mapping nil, nil, true, Nodes::Mapping::BLOCK
          o.instance_variables.each do |ivar|
            accept ivar
            accept o.instance_variable_get ivar
          end
          @emitter.end_mapping

          @emitter.end_mapping
        else
          tag = "!ruby/hash:#{o.class}"
          node = @emitter.start_mapping(nil, tag, false, Psych::Nodes::Mapping::BLOCK)
          register(o, node)
          o.each do |k,v|
            accept k
            accept v
          end
          @emitter.end_mapping
        end
      end