class Psych::Visitors::YAMLTree

def visit_Object o
  tag = Psych.dump_tags[o.class]
  unless tag
    klass = o.class == Object ? nil : o.class.name
    tag   = ['!ruby/object', klass].compact.join(':')
  end
  map = @emitter.start_mapping(nil, tag, false, Nodes::Mapping::BLOCK)
  register(o, map)
  dump_ivars o
  @emitter.end_mapping
end