class Psych::Visitors::YAMLTree

def accept target
  # return any aliases we find
  if @st.key? target
    oid         = @st.id_for target
    node        = @st.node_for target
    anchor      = oid.to_s
    node.anchor = anchor
    return @emitter.alias anchor
  end
  if target.respond_to?(:to_yaml)
    begin
      loc = target.method(:to_yaml).source_location.first
      if loc !~ /(syck\/rubytypes.rb|psych\/core_ext.rb)/
        unless target.respond_to?(:encode_with)
          if $VERBOSE
            warn "implementing to_yaml is deprecated, please implement \"encode_with\""
          end
          target.to_yaml(:nodump => true)
        end
      end
    rescue
      # public_method or source_location might be overridden,
      # and it's OK to skip it since it's only to emit a warning
    end
  end
  if target.respond_to?(:encode_with)
    dump_coder target
  else
    send(@dispatch_cache[target.class], target)
  end
end