class Psych::Visitors::YAMLTree

def dump_coder o
  @coders << o
  tag = Psych.dump_tags[o.class]
  unless tag
    klass = o.class == Object ? nil : o.class.name
    tag   = ['!ruby/object', klass].compact.join(':')
  end
  c = Psych::Coder.new(tag)
  o.encode_with(c)
  emit_coder c, o
end